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Transformation - class-X

Description: transformation
Number of Questions: 65
Created by:
Tags: position and movement vectors and transformations maths transformation and symmetry in geometrical shapes
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The line $3x-4y+7=0$ is rotated through an angle $\dfrac {\pi}{4}$ in clockwise direction about the point $\left (1,1\right)$. The equation of the line in its new position is

  1. $7y+x-6=0$

  2. $7y-x-6=0$

  3. $x+7y=8$

  4. $7y-x+6=0$


Correct Option: A
Explanation:

Given slope $=\dfrac{3}{4} < 1$
$< 45^{o}$
$\therefore $ after rational clock slope because negative
$\dfrac{m _1-m _{2}}{1+m _{1},m _{2}}=\tan 45$
$m _{1}=\dfrac{3}{4} \,\,\,m _{2}=$ new slope
$\left| \dfrac{\dfrac{3}{4}-m}{1+\dfrac{3}{4} m} \right|=1$
$\dfrac{3}{4}-m= \pm \left( 1+\dfrac{3}{4}m \right)$
$\dfrac{3}{4}-m=1+ \dfrac{3}{4} m$
$\dfrac{7}{4}m=\dfrac{-1}{4}$
$m=\dfrac{-1}{7}$ appeared 
$\therefore$ satisfy slope and pt in option to save time.

Let $\displaystyle A\equiv \left( 2,0 \right) $ and $\displaystyle B\equiv \left( 3,1 \right) $. The line $\displaystyle AB$ turns about $\displaystyle A$ through an angle $\displaystyle \frac { \pi  }{ 12 } $ in the clockwise sense, and the new position of $\displaystyle B$ is $\displaystyle B'$. Then $\displaystyle B'$ has the co-ordinates :-

  1. $\displaystyle \left( \frac { 2\sqrt { 2 } -\sqrt { 3 } }{ \sqrt { 2 } } ,\frac { 1 }{ \sqrt { 2 } } \right) $

  2. $\displaystyle \left( \frac { 2\sqrt { 2 } +\sqrt { 3 } }{ \sqrt { 2 } } ,\frac { 1 }{ \sqrt { 2 } } \right) $

  3. $\displaystyle \left( \frac { \sqrt { 3 } -2\sqrt { 2 } }{ \sqrt { 2 } } ,\frac { 1 }{ \sqrt { 2 } } \right) $

  4. $\displaystyle \left( \frac { \sqrt { 3 } -2\sqrt { 2 } }{ 2 } ,\frac { 1 }{ \sqrt { 2 } } \right) $


Correct Option: B
Explanation:

Slope of the line $\displaystyle AB=\frac { 0-1 }{ 2-3 } =1$
$\therefore \angle BAX={ 45 }^{ o }$
Given $\angle B'AB={ 15 }^{ o }\Rightarrow \angle B'AX={ 30 }^{ o }$
Therefore slope of the line $\displaystyle AB'=\tan { { 30 }^{ o } } =\frac { 1 }{ \sqrt { 3 }  } $
Now line $AB'$ makes an angle of ${ 30 }^{ o }$ with positive direction of $x$-axis and 
$AB'=AB=\sqrt { { \left( 3-2 \right)  }^{ 2 }+{ \left( 1-0 \right)  }^{ 2 } } =\sqrt { 2 } $
Therefore coordinates are $\displaystyle \left( 2+\sqrt { 2 } \cos { { 30 }^{ o } } ,0+\sqrt { 2 } \sin { { 30 }^{ o } }  \right) =\left( \frac { 2\sqrt { 2 } +\sqrt { 3 }  }{ \sqrt { 2 }  } ,\frac { 1 }{ \sqrt { 2 }  }  \right) $

Without changing the direction of coordinates axes,  origin is transferred to $(\alpha ,\ \beta)$ so that linear term in the equation $x^{2}+y^{2}+2x-4y+6=0$ are eliminated the point $(\alpha ,\ \beta)$ is   

  1. $(-1,\ 2)$

  2. $(1,\ -2)$

  3. $(1,\ 2)$

  4. $(-1,\ -2)$


Correct Option: B

The point $\mathrm{A}(2,1)$ is translated parallel to the line $x-y=3$ by a distance $4$ units. If the new position $A'$ is in third quadrant, then the coordinates of $A'$ are:

  1. $(2+2\sqrt{2},2+2\sqrt{2})$

  2. $(-2+\sqrt{2},-1-2\sqrt{2})$

  3. $(2-2\sqrt{2},1-2\sqrt{2})$

  4. $(-2-\sqrt{2},-1-2\sqrt{2})$


Correct Option: C
Explanation:

$ y = x-3$ $\Rightarrow m=1$ ; $tan \theta =1$
By parametrization we have $x=2 \pm r cos\theta $
$y=1 \pm r sin\theta $

$x =2 \pm 4\times \dfrac{1}{\sqrt{2}} ;\ y=1 \pm 4\times \dfrac{1}{\sqrt{2}}$.....(consider -ive sign for third quadrant)
$x=2-2\sqrt{2};\ y=1-2\sqrt{2}$ since they are in third quadrant.

If the points $(5, 5), (7, 7)$ and $(a, 8)$ are collinear then the value of a is

  1. $6$

  2. $3$

  3. $8$

  4. $7$


Correct Option: C
Explanation:

When three points are collinear, Slope of line joining any two points is same as the slope of line joining any other two points


Slope of line joining two points $ ({x} _{1}, {y} _{1}) $ and $ ({x} _{2}, {y} _{2}) $ is $\dfrac { {y} _{2} - {y} _{1}}{ {x} _{2} - {x} _{1}} $

So, Slope of line joining $ (5,5) ;  (7,7) $ is $ \dfrac {7-5}{7-5} = \dfrac {2}{2} = 1 $

And Slope of line joining $ (a,8) ;  (7,7) $ is $ \dfrac {7-a}{7-8} = a - 7 $

As they are collinear $ a - 7 = 1 => a = 8 $



${A}$ line has intercepts $ a$ and ${b}$ on the co ordinate axes. When the axes are rotated through an angle $\alpha$, keeping the origin fixed, the line makes equal intercepts on the coordinate axes, then $\tan\alpha=$ 

  1. $\displaystyle \frac{{a}+b}{{a}-b}$

  2. $\displaystyle \frac{{a}-b}{{a}+b}$

  3. $\dfrac{b}{a}$

  4. $\displaystyle \frac{{a}}{b}$


Correct Option: B
Explanation:
Let the equation of line be $ \displaystyle \frac{x}{a}+\frac{y}{b}=1.$

When axes are rotated through an angle $ \alpha$, the new coordinates $XY$ are related to old coordinates $xy$ as follows:

$x=X \cos\alpha -Y\sin \alpha $

$y=X \sin\alpha +Y\ \cos \alpha $

Substituting these values in the equation of line, we get
$ \displaystyle \frac { X\cos { \alpha  } -Y\sin { \alpha  }  }{ a } +\frac { X\sin { \alpha  } +Y\cos { \alpha  }  }{ b } =1\\ \displaystyle \Rightarrow X\left( \frac { \cos { \alpha  }  }{ a } +\frac { \sin { \alpha  }  }{ b }  \right) +Y\left( \frac { \cos { \alpha  }  }{ b } -\frac { \sin { \alpha  }  }{ a }  \right) =1$

As it makes equal intercepts in the new coordinate system, we get

$ \displaystyle \Rightarrow \frac{\cos \alpha }{a}+\frac{\sin \alpha }{b}=\frac{\cos \alpha }{b}-\frac{\sin \alpha }{a}$

$\Rightarrow \cos \alpha \left ( b-a \right )=-\sin \alpha \left ( a+b \right )$

$ \displaystyle \Rightarrow \tan  \alpha =\dfrac{a-b}{a+b}$

The angle of rotation of the axes so that the equation $\sqrt{3}\mathrm{x}-\mathrm{y}+5=0$ may be reduced to the form $\mathrm{Y}=\mathrm{k}$, where $\mathrm{k}$ is a constant is 

  1. $\dfrac{\pi}{6}$

  2. $\dfrac{\pi}{4}$

  3. $\dfrac{\pi}{3}$

  4. $\dfrac{\pi}{12}$


Correct Option: C
Explanation:
Let axis be rotated through an angle $\theta $ then 
$ x= x^{1} \cos \theta - y^{1} \sin\theta $
$ y = x^{1} \sin \theta + y^{1} \cos\theta $
$ \sqrt{3}\times x -y +5 = 0$
$ \sqrt{3} (x^{1} \cos \theta - y^{1} \sin\theta) - (x^{1} \sin \theta + y^{1} \cos\theta) +5 = 0$
$x^{1} (\sqrt{3} \cos \theta - \sin\theta ) = 0$
$ \Rightarrow \tan\theta  = \sqrt{3}$
$ \theta = 60^{\circ} = \dfrac{\pi }{3}$

Find the equation of a line whose inclination is $\displaystyle 30^{\circ}$ and making an intercept of -3/5 on the y-axis

  1. $ y = \dfrac {5}{\sqrt{6}}x  +\dfrac {2}{5} $

  2. $ y = \dfrac {1}{\sqrt{3}}x  -\dfrac {3}{5} $

  3. $ y = \dfrac {3}{\sqrt{7}}x  -\dfrac {1}{3} $

  4. $\displaystyle \dfrac{-5}{3}x$


Correct Option: B
Explanation:

The equation of any straight line can be written as $ y = mx + c $, where $m$ is its slope and $c$ is its y - intercept.

As inclination is $ 30^o $, slope of the line $ =  tan (30 ^o) = \dfrac {1}{\sqrt{3}} $

So equation of line is $ y = \dfrac {1}{\sqrt{3}}x  -\dfrac {3}{5} $

lf the equation $4\mathrm{x}^{2}+2\sqrt{3}\mathrm{x}\mathrm{y}+2\mathrm{y}^{2}-1=0$ becomes $5\mathrm{X}^{2}+\mathrm{Y}^{2}=1$, when the axes are rotated through an angle $\theta$, then $\theta$ is 

  1. $15^{\mathrm{o}}$

  2. $30^{\mathrm{o}}$

  3. $45^{0}$

  4. $60^{\mathrm{o}}$


Correct Option: B
Explanation:
By  rotation  of  axes  through  $\theta $,  co-ordinates  become
$x = x^{1}  \cos\theta  - y^{1}  \sin\theta $
$y = x^{1}  \sin\theta  + y^{1}  \cos\theta $
$4x^{2} + 2\sqrt{3}xy + 2y^{2} - 1=0$
$\Rightarrow 4(x^{1}\cos\theta - y^{1} \sin\theta )^{2} + 2\sqrt{3} (x^{1} \cos\theta  -y^{1} \sin\theta )  (x^{1} \sin\theta + y^{1} \cos\theta )  +2 (x^{1}\sin\theta +y^{1} \cos\theta )^{2} -1 =0$
coeff  of $xy=0$
$\Rightarrow 4(-\sin2\theta )+2\sqrt{3}   \cos20  +  2 \sin2\theta  = 0$
$2\sqrt{3}   \cos2\theta  = 2\sin2\theta $
$\tan2\theta = \sqrt{3}$
$2\theta = \dfrac{\pi }{3}$
$\theta  = \dfrac{\pi }{6} = 30^{\circ}$
$\therefore $ angle  to  be  rotated $= 30^{\circ}$

lf the distance between two given points is $2$ units and the points are transferred by shifting the origin to $(2, 2)$, then the distance between the points in their new position is.

  1. $2$

  2. $5$

  3. $6$

  4. $7$


Correct Option: A
Explanation:

Shifting the origin to $(2 , 2)$ transforms the coordinates to
$(x , y)$ to $(x - 2, y - 2)$.

$\therefore$ distance between two points is

$\sqrt{(x _{1}-x _{2})^{2}+(y _{1}-y _{2})^{2}}$

$=\sqrt{((x _{1}-2)-(x _{2}-2))^{2}+((y _{1}-2)-(y _{2}-2))}^{2}$

$=\sqrt{(x _{1}-x _{2})^{2}+(y _{1}-y _{2})}^{2}$

$\therefore$ distance is unaltered $ = 2$ units.

If a point $\mathrm{P}(4,3)$ is shifted by a distances $\sqrt{2}$ units parallel to the line $\mathrm{y}=\mathrm{x}$, then the coordinates of $\mathrm{P}$ in its new position are

  1. $(5,4)$

  2. $(5+\sqrt{2},4+\sqrt{2})$

  3. $(5-\sqrt{2},4-\sqrt{2})$

  4. $(4,5)$


Correct Option: A
Explanation:

shifted by $\sqrt{2}$ units $\Rightarrow r=\sqrt{2}$

for the line is tan $\theta =1$

$\therefore$ by parametric equations, we have

$x=x^{1}+r\ cos \theta$ ;  $y=y^{1}+r\ sin \theta$

$\Rightarrow x=4+\sqrt{2}\frac{1}{\sqrt{2}}$ ; $y=3+\sqrt{2}\frac{1}{\sqrt{2}}$

$x=5$  ;  $y=4$

A line has intercepts a, b on the coordinate axes. If the axes are rotated about the origin through an angle $\displaystyle \alpha$ then the line has intercepts p,q on the new position of the axes respectively. Then 

  1. $\displaystyle \frac{1}{p^{2}}+\frac{1}{q^{2}}=\frac{1}{a^{2}}+\frac{1}{b^{2}}$

  2. $\displaystyle \frac{1}{p^{2}}-\frac{1}{q^{2}}=\frac{1}{a^{2}}-\frac{1}{b^{2}}$

  3. $\displaystyle \frac{1}{p^{2}}+\frac{1}{a^{2}}=\frac{1}{q^{2}}+\frac{1}{b^{2}}$

  4. None of these


Correct Option: A
Explanation:

Since the line has intecepts a and b on the coordinate axes, therefore its equation is 
$\cfrac { x }{ a } +\cfrac { y }{ b } =1$
When the axes are rotated, its equation with respect to the new axes and the same origin will become
$\cfrac { x }{ p } +\cfrac { y }{ q } =1$
In both the cases, the length of the perpendicular from the origin to the line will be same
Therefore
$\cfrac { 1 }{ \sqrt { \cfrac { 1 }{ { a }^{ 2 } } +\cfrac { 1 }{ { b }^{ 2 } }  }  } =\cfrac { 1 }{ \sqrt { \cfrac { 1 }{ { p }^{ 2 } } +\cfrac { 1 }{ { q }^{ 2 } }  }  } \ \Rightarrow \cfrac { 1 }{ { a }^{ 2 } } +\cfrac { 1 }{ { b }^{ 2 } } =\cfrac { 1 }{ { p }^{ 2 } } +\cfrac { 1 }{ { q }^{ 2 } } $

If the origin is shifted to the point $(\displaystyle\frac{ab}{a-b}, 0)$ without rotation, then the equation $(a-b)(x^2 + y^2) - 2abx = 0$ becomes

  1. $(a-b) (X^2+Y^2) - (a+b)XY + abX = a^2$

  2. $(a+b) (X^2 + Y^2) = 2ab$

  3. $(X^2 + Y^2) = (a^2 + b^2)$

  4. $(a-b)^2 (X^2 + Y^2) = a^2 b^2$


Correct Option: D
Explanation:

The given equation is 
$(a-b) (x^2 + y^2) - 2abx = 0$             ........... (i)
The origin is shifted to (ab/(a-b), 0). Any point (x, y) on the curve (i) must be replaced with a new point (X, Y) with reference to new axes, such that
$\displaystyle x = X + \frac{ab}{a-b}  ,\    y = Y +0$
substituting these in (i), we get
$(a-b) \displaystyle \left [ \left (X + \frac{ab}{a-b} \right )^2 + y^2 \right ] - 2ab \left [ X+ \frac{ab}{a-b} \right ] = 0$
$\Rightarrow (a-b) \displaystyle \left [ X^2 + \frac{a^2 b^2}{(a-b)^2} + Y^2 + \frac{2abX}{a-b} \right ] - 2abX - \frac{2a^2 b^2}{a-b} = 0$
$\Rightarrow (a-b) (X^2 + Y^2) = \displaystyle \frac{a^2 b^2}{a-b}$
$\Rightarrow (a-b)^2 (X^2+Y^2) = a^2 b^2$

The new equation of the curve $4(x-2y+1)^{2}+9(2x+y+2)^{2}=25$ if the lines $2x+y+2=0$ and $x-2y+1=0$ are taken as the new $x$ and $y$ axes respectively is

  1. $4X^{2}+9Y^{2}=5$

  2. $4X^{2}+9Y^{2}=25$

  3. $4X^{2}+9Y^{2}=7$

  4. $4X^{2}-9Y^{2}=7$


Correct Option: A

The coordinates axes are rotated about the origin $O$ in the counter clockwise direction through an angle of $\dfrac{\pi}{6}$. If $a$ and $b$ are intercepts made on the new axes by a straight line whose equation referred to old the axes is $x+y=1$, then the value of $\displaystyle \frac{1}{a^{2}}+\displaystyle \frac{1}{b^{2}}$ is equal to

  1. $1$

  2. $2$

  3. $4$

  4. $\dfrac{1}{2}$


Correct Option: B
Explanation:

Given equation is $x+y=1$
We know that 
$\displaystyle x=X\cos\theta-Y\sin\theta$
$y=X\sin\theta+Y\cos\theta$
$\Rightarrow (\cos\theta+\sin\theta)X+(\cos\theta-\sin\theta)Y=1$  
$\displaystyle \Rightarrow \frac{(\sqrt{3}+1)}{2}X+ \frac{(1-\sqrt{3})}{2}Y=1$       .....(i)
According to problem, we have

$\displaystyle\frac{X}{a}+\frac{Y}{b}=1$ .....(ii)
$\displaystyle\Rightarrow \frac { 1 }{ a } =\frac { (\sqrt { 3 } +1) }{ 2 } $
$\Rightarrow \displaystyle \frac { 1 }{ b } =\frac { (1-\sqrt { 3 } ) }{ 2 } $
So, $\displaystyle \frac { 1 }{ { a }^{ 2 } } +\frac { 1 }{ { b }^{ 2 } } =2$

The reflection of the plane $x+y+z-3=0$ in the plane $2x+3y+4z-6=0$

  1. $1/6$

  2. $\sqrt6$

  3. $4x+3y-2z+15=0$

  4. None of these


Correct Option: B

Reflection of the line $\dfrac{x-1}{-1}=\dfrac{y-2}{3}=\dfrac{z-4}{1}$ in the plane $x+y+z=7$ is:

  1. $\dfrac{x-1}{3}=\dfrac{y-2}{1}=\dfrac{z-4}{1}$

  2. $\dfrac{x-1}{-3}=\dfrac{y-2}{-1}=\dfrac{z-4}{1}$

  3. $\dfrac{x-1}{-3}=\dfrac{y-2}{1}=\dfrac{z-4}{-1}$

  4. $\dfrac{x-1}{3}=\dfrac{y-2}{1}=\dfrac{z-4}{-2}$


Correct Option: B

The image of the line $x-y-1=0$ in the line $2x-3y+1=0$ is

  1. $7x-17y+23=0$

  2. $17x-7y+23=0$

  3. $7x+17y+23=0$

  4. $ 17x+7y+23=0$


Correct Option: A

The image of the point A$(1,2)$ by the line mirror y=x and the image of B by the line mirror $y=0$ is the point $\left(\alpha, \beta \right)$, then :

  1. $\alpha =1,\beta =-2$

  2. $\alpha =0,\beta =0$

  3. $\alpha =2,\beta =-1$

  4. None of these


Correct Option: C

A ray of light travelling along the line $x+\sqrt{3}y=5$ is incident on the $x-axis$ and after refraction it enters the other side of the $x-axis$ by turning $\dfrac{\pi}{6}$ away from the $x-axis$. The equation of the line along which the refracted ray travels is

  1. $x+\sqrt{3}y-5\sqrt{3}=0$

  2. $x-\sqrt{3}y-5\sqrt{3}=0$

  3. $\sqrt{3}x+y-5\sqrt{3}=0$

  4. $\sqrt{3}-y-5\sqrt{3}=0$


Correct Option: A

If $B$ is reflection of $A(a,5)$ about line $4x-3y=0$, then area of triangle $ABC$ is equal to

  1. $\dfrac{253}{50}$

  2. $\dfrac{506}{25}$

  3. $\dfrac{253}{25}$

  4. $\dfrac{506}{50}$


Correct Option: A

Locus of the image of the point (2, 3) in the line (2x - 3y + 4) + k(x - 2y + 3) = 0, k $\in $ R, is a 

  1. straight line parallel to x-axis

  2. straight line parallel to y-axis

  3. Circle of radius $\sqrt { 2 } $

  4. circle of radius 3


Correct Option: A

The distance of the image of a point (or an object) from the line of symmetry (mirror) is  ----- as that of the point (object )from the line (mirror).

  1. same 

  2. double

  3. triple

  4. none


Correct Option: A
Explanation:
To make the above statement true, the word to be placed in the blank is : “same”
So, the true statement becomes :
The distance of the image of a point (or an object) from the line of symmetry (mirror) is same as that of the point (object) from the line (mirror).
Hence, option A is the correct answer.

The image of the point (-5,4) under a reflection across the y-axis is (5,4).

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient


Correct Option: A

Image of $\left (1,2\right)\ w.r.t\left (-2,-1\right)$ is

  1. $\left (0,5\right)$

  2. $\left (-4,-3\right)$

  3. $\left (-4,-2\right)$

  4. $\left (-4,-5\right)$


Correct Option: D

If the line $\left (2\cos \theta+ 3\sin \theta\right)$ $x+(\left (3\cos \theta- 5\sin \theta\right)$ $y-\left (5\cos \theta- 2\sin \theta\right)=0$ passes through a fixed point $P$ for all values $\theta$ and $Q$ be the image of the point $P$ with the respect to the line $4x+6y-23=0$, then the distance of $Q$ from the origin is:

  1. $\dfrac {13}{5}$

  2. $\sqrt {5}$

  3. $5\sqrt {2}$

  4. $5$


Correct Option: A

The image of the point $A(1,2)$ by the line mirror  $y=x$ is the 
Point B and the image of B by the line mirror $y=0$ is the point $(a,\beta )then:$ 

  1. $a = -2,\beta = - 1$

  2. $a = 0,\beta = 0$

  3. $a = 2,\beta = - 1$

  4. none of these


Correct Option: A

A ray of light along $x + \sqrt {3y}  = \sqrt 3 $ gets reflected upon reaching $x - axis$ , then equation of the reflected ray is 

  1. $y = x + \sqrt 3 $

  2. $\sqrt 3 y = x - \sqrt 3 $

  3. $y = \sqrt 3 x - \sqrt 3 $

  4. $\sqrt 3 y = x - 1$


Correct Option: B
Explanation:
Mirror or reflecting surface/ boundary is $y = 0$ or $x-axis$.

Light Ray: $x + \sqrt3 y = \sqrt3$ or,
$\sqrt 3 y = \sqrt3 - x$.

Slope: $m = \dfrac{-1}{\sqrt3}$. Meets x axis at $A(\sqrt3, 0)$.

The reflected ray will have a slope$ = - m = \dfrac{1}{\sqrt3}$. Reason is that the angle of inclination with x axis becomes 180 - the angle of incident ray.

Also it passes through point $A$.

So the equation is: $y - 0 =\dfrac{ (x - \sqrt3)}{ \sqrt3}.$
Or, $\sqrt3 y - x + \sqrt3 = 0$.
Or, $\sqrt3 y=x-\sqrt3$

The line segment joining $A\left( {3,\,\,0} \right),\,\,B\left( {5,\,\,2} \right)$ is rotated about a point A in anticlockwise sense through an angle $\displaystyle{\pi  \over 4}$ and B move to C. If a point D be the reflection of C in y-axis, then D=

  1. $\left( { - 3,\,2\sqrt 2 } \right)$

  2. $\left( {3,\,2\sqrt 2 } \right)$

  3. $\left( {3,\, - 2\sqrt 2 } \right)$

  4. $\left( {3,\,8\sqrt 2 } \right)$


Correct Option: A
Explanation:
$A(3, 0)$ and $B(5, 2)$
Slope of AB$=\dfrac{2-0}{5-3}=1$
Then, if $\theta$, is the angle made by AB, with positive direction of x-axis, we have $\tan\theta =1$
$\Rightarrow \theta =45^o$
Given, AB is rotated by $45^o$ to AC
Now AB$=\sqrt{(3-5)^2+(0-2)^2}=2\sqrt{2}$
So, coordinate of pr w$(3, 2\sqrt{2})$
Hence reflection of c in y-axis is $(-3, 2\sqrt{2})$.

The reflection of the point $(2, -1, 3)$ in the plane $3x-2y-z=9$ is?

  1. $\left(\dfrac{26}{7}, \dfrac{15}{7}, \dfrac{17}{7}\right)$

  2. $\left(\dfrac{26}{7}, \dfrac{-15}{7}, \dfrac{17}{7}\right)$

  3. $\left(\dfrac{16}{7}, \dfrac{26}{7}, \dfrac{-17}{7}\right)$

  4. $\left(\dfrac{1}{6}, \dfrac{2}{3}, \dfrac{3}{4}\right)$


Correct Option: A

Find the image of the point $\displaystyle \left ( -2, -7 \right )$ under the transformation
$\left ( x, y \right )\rightarrow \left ( x-2y,-3x+y \right ).$

  1. $\displaystyle \left ( 12, -1 \right )$

  2. $\displaystyle \left ( -12, 1 \right )$

  3. $\displaystyle \left ( 2, 7 \right )$

  4. $\displaystyle \left ( -2, 7 \right )$


Correct Option: A
Explanation:

Given transformation is 
$\left ( x, y \right )\rightarrow \left ( x-2y,-3x+y \right )$
So, the point $(-2,-7)$ $\rightarrow (-2-2(-7),-3(-2)-7)$
So, the image of the point $(-2,-7)$ under the given transformation is $ (12,-1)$

If $(-2, 6)$ is the image of the point $(4, 2)$ with respect to the line $L =$ $0$, then $L =$

  1. $6x - 4y -7 =0$

  2. $2x + 3y -5 =0$

  3. $3x - 2y + 5 =0$

  4. $3x - 2y + 10=0$


Correct Option: C
Explanation:

Let points are $A(-2,6)$ & $B(4,2)$

$\therefore$    $L=0$ is $\bot $ to $AB$ & passes through the mid point slope $AB=\dfrac { -4 }{ 6 } =\dfrac { -2 }{ 3 } $
$\therefore$    slope of $L=0=3/2$
passes through $(1,4)$
$\therefore$    required equation is $\left( y-4 \right) =\frac { 3 }{ 2 } \left( x-1 \right) $
                                     $\Rightarrow 2y-8=3x-3$
                                     $\Rightarrow 3x-2y+5=0$        [C]

The image of the pair of lines represented by$\displaystyle :ax^{2}+2hxy+by^{2}= 0 $ by the line $ y= 0 $ mirror is:

  1. $\displaystyle :ax^{2}-2hxy-by^{2}= 0$

  2. $\displaystyle :bx^{2}-2hxy+ay^{2}= 0$

  3. $\displaystyle :bx^{2}+2hxy+ay^{2}= 0$

  4. $\displaystyle :ax^{2}-2hxy+by^{2}= 0$


Correct Option: D
Explanation:

In ${ ax }^{ 2 }+2hxy+{ by }^{ 2 }=0 $ replacing $y$ by $-y$
we get, ${ ax }^{ 2 }+2hx\left( -y \right) +{ by }^{ 2 }=0 $
$\Rightarrow { ax }^{ 2 }-2hxy+{ by }^{ 2 }=0 $

The coordinates of the image of the origin $O$ with respect to the line $x+y+1=0$ are

  1. $\left ( \displaystyle -\frac{1}{2},\displaystyle -\frac{1}{2} \right )$

  2. $(-2,-2)$

  3. $(1,1)$

  4. $(-1,-1)$


Correct Option: D
Explanation:

Let $Q(h,k)$ be the image of $O(0,0)$ w.r.t the line mirror $x+y+1=0$

$\displaystyle \frac{h-0}{1}=\frac{k-0}{1}=\frac{-2(1)}{2}$

$\displaystyle \Rightarrow h=k=-1$

$\Rightarrow h=-1, k=-1$
So, the image is at $(-1,-1)$

The equation of the line AB is y = x. if And B lie on the same side of the line mirror 2x - y = 1, then the equation of the image of AB is   _____________.

  1. x + y - 2 = 0

  2. 8x + y - 9 = 0

  3. 7x - y - 6 = 0

  4. none of these


Correct Option: C

The image of the point $A(1, 2)$ by the line mirror $y=x$ is the point $B$ and the image of $B$ by the line mirror $y=0$ is the point $(\alpha, \beta)$, then?

  1. $\alpha =1, \beta =-2$

  2. $\alpha =0, \beta =0$

  3. $\alpha =2, \beta =-1$

  4. $\alpha =1, \beta =-1$


Correct Option: C

$P(2,1)$ is image of the point $Q(4,3)$ about the line

  1. $x+y=3$

  2. $x-y=1$

  3. $3x+y=5$

  4. $-x+2y=0$


Correct Option: B

The point $P(2, 1)$ is shifted by $\displaystyle 3\sqrt{2}$ parallel to the line $\displaystyle x+y=1,$ in the direction of increasing ordinate, to reach $Q$.The image of $Q$ by the line $\displaystyle x+y=1$ is

  1. $\displaystyle (5,-2)$

  2. $\displaystyle (-1,4)$

  3. $\displaystyle (3,-4)$

  4. $\displaystyle (-3,2)$


Correct Option: D
Explanation:

The point $P(2,1)$ if shifted by $3\sqrt2$ parallel to the line $x+y =1$, in the direction of increasing ordinate, to reach point $Q(\alpha, \beta)$.


The equation of line produced from $P(2,1)$ to $Q(\alpha, \beta)$ parallel to line $x+y = 1$ in parametric form is,

$\Rightarrow \dfrac { \alpha -2}{cos \theta} = \dfrac{ \beta -1}{sin \theta} = -3\sqrt2$   .....$(1)$

Where $\theta$ is slope of line $PQ$, which is parallel to line $x +y = 1$

Hence Slope of $PQ$ $= -1$

$\Rightarrow\text{ if} \   tan \theta = -1 $

$\Rightarrow cos \theta = \dfrac {1}{\sqrt2}$

$\Rightarrow sin \theta = - \dfrac{1}{\sqrt2}$

Hence from equation $(1)$, $\alpha = -1, \beta = 4$ and $Q(-1,4)$

Now image of $Q(-1,4)$ in the line $x+y = 1$ is given by,

$\Rightarrow \dfrac {x - x _1 } {a} = \dfrac{y -y _1} {b} = \dfrac {-2 (ax _1 +by _1 +c)}{a^2 +b^2} $

$\Rightarrow \dfrac{x+1}{1} = \dfrac{y-4}{1} = \dfrac {-2 (-1 +4 -1)}{1^2 +1^2}$

Hence $x = -3$ and $y = 2$

Correct option is $D$.

The image of the line $\displaystyle  \frac { x - 1 } { 3 } = \frac { y - 3 } { 1 } = \frac { z - 4 } { - 5 } $ in the plane $2 x - y + z + 3 = 0 $ is the line

  1. $

    \displaystyle\frac { x + 3 } { 3 } = \frac { y - 3 } { 1 } = \frac { z - 2 } { - 5 }

    $

  2. $\displaystyle 

    \frac { x + 3 } { - 3 } = \frac { y - 5 } { - 1 } = \frac { z + 2 } { 5 }

    $

  3. $\displaystyle 

    \frac { x - 3 } { 3 } = \frac { y + 5 } { 1 } = \frac { z - 2 } { - 5 }

    $

  4. $\displaystyle 

    \frac { x - 3 } { - 3 } = \frac { y + 5 } { - 1 } = \frac { z - 2 } { 5 }

    $


Correct Option: A
Explanation:
Let $A\left(1,3,4\right)$ be a point.

Let $M$ be the point on the plane.

Given equation of the plane is $2x-y+z+3=0$

Thus, the equation of the plane is

$\dfrac{x-1}{2}=\dfrac{y-3}{-1}=\dfrac{z-4}{3}=k$

Any point on the above line, $AM$ is of the form

$x=2k+1,y=-k+3,z=k+4$

Substituting the above values in the equation of the plane we have

$2\left(2k+1\right)-\left(-k+3\right)+\left(k+4\right)+3=0$

$\Rightarrow\,4k+2+k-3+k+4+3=0$

$\Rightarrow\,6k+6=0$

$\Rightarrow\,k=-1$

Thus the coordinates of $M$ are

$x=2\times -1+1=-2+1=-1$

$y=-\left(-1\right)+3=1+3=4$

$z=-1+4=3$

Let $B\left({x}^{\prime},{y}^{\prime},{z}^{\prime}\right)$ be the image of $A$

Thus, $M$ is the midpoint of $AB$

$\therefore\,-1=\dfrac{1+{x}^{\prime}}{2},\,4=\dfrac{3+{y}^{\prime}}{2},\,3=\dfrac{4+{z}^{\prime}}{2}$ 

$\Rightarrow\,1+{x}^{\prime}=-2,\,\,3+{y}^{\prime}=8,\,\,4+{z}^{\prime}=6$

$\Rightarrow\,{x}^{\prime}=-2-1=-3,\,\,{y}^{\prime}=8-3=5,\,\,{z}^{\prime}=6-4=2$

$\therefore\,\dfrac{x+3}{3}=\dfrac{y-3}{1}=\dfrac{z-2}{-5}$

Hence the image of the given line.

The point (4, 1) undergoes the following transformation successively.
(i)reflection about the line y=x
(ii)translation through a distance 2 units along the positive direction of x-axes.
(iii)rotation through an angle ${ \pi  }/{ 4 }$ about the origin in the anticlockwise direction.
(iv) reflection about x=0
The final position of the given point is

  1. $(1\sqrt { 2 } ,7/2)$

  2. $(1/2,7\sqrt { 2 } )$

  3. $(1\sqrt { 2 } ,7/\sqrt { 2 } )$

  4. $(1/2,7/2)$


Correct Option: A

Let  $ABC$ be triangle. Let $A$ be the point $(1,2),y=x$be the perpendicular bisector of $AB$ and $x-2y+1=0$ be the angle bisector of $\angle C$. If equation of $BC$ is given by $ax+by-5=0$, then the value of $a+b$ is 

  1. $1$

  2. $2$

  3. $3$

  4. $4$


Correct Option: B
Explanation:

$\begin{array}{l} { m _{ AB } }=-1 \ y-2=-1\left( { x-1 } \right)  \ y-2=-x+1 \ x+y=3 \ \underline { x-y=0 }  \ 2x=3 \ \therefore x=\frac { 3 }{ 2 } \, \, \, \, \, ,y=\frac { 3 }{ 2 }  \ \frac { { 1+h } }{ 2 } =\frac { 3 }{ 2 } \, \, \,  \ h=2 \ \frac { { 2+k } }{ 2 } =\frac { 3 }{ 2 }  \ k=1\, \, \, \, \, \, \, \, \, \, \, B\left( { 2,1 } \right)  \ As\, \, image\, \, through\, \, x-2y+1=0 \ { m _{ AD } }=-2 \ y-2=-2\left( { x-1 } \right)  \ y-2=-2x+2 \ 2x+y=4\times 2\, \, \, \, \, \, \, x-2y+1=0 \ 4x+2y=8 \ \underline { x-2y=-1 }  \ 5x=7 \ x=\frac { 7 }{ 5 } \, \, \, \, \, \, y=\frac { { x+1 } }{ 2 } =\frac { { 12 } }{ { 5\times 2 } } =\frac { 6 }{ 5 }  \ \frac { { m+1 } }{ 2 } =\frac { 7 }{ 5 } \, \, \, \, \, \, \, \, \frac { { n+1 } }{ 2 } =\frac { 6 }{ 5 }  \ m+1=\frac { { 14 } }{ 5 } \, \, \, \, \, \, \, n+2=\frac { { 12 } }{ 5 }  \ m=\frac { 9 }{ 5 } \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, n=\frac { { 12 } }{ 5 } -2=\frac { 2 }{ 5 }  \ E\left( { \frac { 9 }{ 5 } ,\frac { 2 }{ 5 }  } \right)  \ BC=BE\, \, \, \, \, \, B\left( { 2,1 } \right) \, \, \, E\left( { \frac { 9 }{ 5 } ,\frac { 2 }{ 5 }  } \right)  \ y-1=\left( { \frac { { 1-\frac { 2 }{ 5 }  } }{ { 2-\frac { 9 }{ 5 }  } }  } \right) \left( { x-2 } \right)  \ 3x-y=5 \ a=3\, \, \, \, b=-1 \ a+b=2 \end{array}$

If the image of the point $ \displaystyle \left ( 4,-6 \right ) $ by a line is the point $(2,2)$, then the equation of the mirror is

  1. $ \displaystyle 4x+3y-5= 0 $

  2. $ \displaystyle x-4y= 11 $

  3. $ \displaystyle x+4y-5= 0 $

  4. $ \displaystyle -x+y+11= 0 $


Correct Option: B
Explanation:

From given points, required line and line joining points are perpendicular to each other,


$\displaystyle \therefore$ slope of required line is $\displaystyle m=-\frac { 2-4 }{ 2-(-6) } =\frac { 1 }{ 4 } $

The midpoint of the given points will be on our line.

$\Rightarrow$$X=\left ( \dfrac{x _1+x _2}{2}\right ) and \ Y=\left ( \dfrac{y _1+y _2}{2}\right )$

$\Rightarrow$$X=\left ( \dfrac{4+2}{2}\right ) =3 \ and \ Y=\left ( \dfrac{-6+2}{2}\right )=-2$

$\displaystyle \therefore$ point is $\displaystyle (3,-2)\equiv(x _1,y _1)$.

$\therefore$ Equation of line is given by, 

$\Rightarrow$$y-y _1=m(x-x _1)$

Then equation of required line is $\displaystyle \frac { y+2 }{ x-3 } =\frac { 1 }{ 4 } \Longrightarrow x-4y=11$

A ray light comming from the point $(1,2)$ is reflected at a point $A$ on the $x-$axis and then passes through the point $(5,3)$. The co-ordinates of the point $A$ is

  1. $\left(\dfrac {13}{5}, 0\right)$

  2. $\left(\dfrac {5}{13}, 0\right)$

  3. $(-7, 0)$

  4. $None\ of\ these$


Correct Option: A

The point $A(4, 1)$ undergoes following transformations successively:
(i) reflection about line $y=x$
(ii) translation through a distance of $3$ units in the positive direction of x-axis.
(iii) rotation through an angle $105^o$ in anti-clockwise direction about origin O.
Then the final position of point A is?

  1. $\left(\dfrac{1}{\sqrt{2}}, \dfrac{7}{\sqrt{2}}\right)$

  2. $(-2, 7\sqrt{2})$

  3. $\left(-\dfrac{1}{\sqrt{2}}, \dfrac{7}{\sqrt{2}}\right)$

  4. $(-2\sqrt{6}, 2\sqrt{2})$


Correct Option: A

The reflection of the point $(4, -13)$ in the line $5x+y+6=0$ is

  1. $(-1, -14)$

  2. $(3,4)$

  3. $(1,2)$

  4. $(-4, 13)$


Correct Option: A

The image of the pair of lines represented by $\displaystyle 3x^{2}+4xy+5y^{2}=0 $ in the line mirror $x = 0$ is

  1. $\displaystyle 3x^{2}-4xy+5y^{2}=0 $

  2. $\displaystyle 3x^{2}-4xy-5y^{2}=0 $

  3. $\displaystyle 5y^{2}-4xy-3x^{2}=0 $

  4. none of these


Correct Option: A
Explanation:

Here the mirror image of line $3x^2+4xy+5y^2=0$ in mirror $x=0$

i.e about $Y-axis $
So the x-coordinates About $Y-axis $ becomes negative and the y-coordiantes remains same Hence putting $x=-x$ in given eq 
$3(-x)^2-4(-x)y+5y^2=0$
$3x^2-4xy+5y^2=0$

The point A(4, 1) undergoes following transformations successively
(i) reflection about line y = x
(ii) translation through a distance of 2 units in the positive direction of x axis
(iii) rotation through an angle $\displaystyle \pi/4 $ in anti clockwise direction about origin O
Then the final position of point A is

  1. $\displaystyle \left ( \frac{1}{\sqrt{2}},\frac{7}{\sqrt{2}} \right ) $

  2. $\displaystyle \left ( -2,7\sqrt{2} \right )$

  3. $\displaystyle \left ( -\frac{1}{\sqrt{2}},\frac{7}{\sqrt{2}} \right )$

  4. none of these


Correct Option: C
Explanation:
Given Point $A(4,1)$
$(i) $ reflection about $y=x$
Hence putting coordinates of point A in given eq $y=4,x=1$
The point becomes $A(1,4)$

$(ii)$ translation through distance of 2 units in positive X axis 
$A(1+2,4)\Rightarrow A(3,4)$

$(iii)$ rotation of point through and angle $\dfrac{\pi}{4}$ in anticlockwise about origin O
After rotation Point will be $A(r\cos(\alpha+\dfrac{pi}{4}),r\sin(\alpha+\dfrac{pi}{4}))$
Converting into polar form 
$r=\sqrt{3^2+4^2}=5$
$\tan\alpha=\dfrac{4}{3}$
Hence $\cos\alpha=\dfrac{3}{5}$
$\sin\alpha=\dfrac{4}{5}$
$\cos(\alpha+\dfrac{\pi}{4})=\cos\alpha\cos\dfrac{\pi}{4}-\sin\alpha\sin\dfrac{\pi}{4}$
$\cos(\alpha+\dfrac{\pi}{4})=\dfrac{3}{5}\dfrac{1}{\sqrt{2}}-\dfrac{4}{5}\dfrac{1}{\sqrt{2}}$
$\cos(\alpha+\dfrac{\pi}{4})=\dfrac{-1}{5\sqrt{2}}$

$\sin(\alpha+\dfrac{\pi}{4})=\sin\alpha\cos\dfrac{\pi}{4}+\cos\alpha\sin\dfrac{\pi}{4}$
$\sin(\alpha+\dfrac{\pi}{4})=\dfrac{4}{5}\dfrac{1}{\sqrt{2}}+\dfrac{3}{5}\dfrac{1}{\sqrt{2}}$
$\sin(\alpha+\dfrac{\pi}{4})=\dfrac{7}{5\sqrt{2}}$
$A\left(5\times \dfrac{-1}{5\sqrt{2}},5\times \dfrac{7}{5\sqrt{2}}\right)$
$A\left(-\dfrac{1}{\sqrt{2}}, \dfrac{7}{\sqrt{2}}\right)$

The co-ordinates of the point of reflection of the origin $(0, 0)$ in the line $4x -2y - 5 = 0$ is

  1. $(-1, 2)$

  2. $(2, -1)$

  3. $\displaystyle \left (\frac {4}{5}, -\frac {2}{5}\right )$

  4. $(2, 5)$


Correct Option: B
Explanation:

Let $(h,k)$ be the point of reflection.
Line joining $(0,0)$ and $(h,k)$ is perpendicular to $4x-2y-5=0$
Product of slopes of these lines is $-1$
$\dfrac{k}h*2=-1=>k=-\dfrac{h}2$
Midpoint of $(0,0)$ and $(h,k)$ i.e, $(\dfrac{h}{2},\dfrac{k}{2})$ lies on $4x-2y-5=0$
Therefore $4\dfrac{h}2-2\dfrac{k}2-5=0=>2h-k-5=0$ but $k=-\dfrac{h}2$
$2h+\dfrac{h}2-5=0=>h=2 $ and $k=-1$
Point of reflection is $(2,-1)$.

The equation of the image of the circle $\displaystyle x^{2}+y^{2}+16x-24y+183=0 $ along the line mirror $4x + 7y + 13 = 0$ is:

  1. $\displaystyle x^{2}+y^{2}+32x-4y+235=0 $

  2. $\displaystyle x^{2}+y^{2}+32x+4y-235=0 $

  3. $\displaystyle x^{2}+y^{2}+32x-4y-235=0 $

  4. $\displaystyle x^{2}+y^{2}+32x+4y+235=0 $


Correct Option: D
Explanation:

The given equation of the circle is $x^2 + y^2 + 16x - 24y + 183 = 0$, which can be written as,


$\Rightarrow (x+8)^2 + (y-12)^2 = (5)^2$

Hence we can see the center of the circle , let's say $O(- 8, 12)$ and radius of the circle is $r = 5$

If we mirror the image of the given circle by the line $4x +7y +13 =0$, the radius of the circle won't change. But the position of center will get change. Let's assume the new center will be $O'( \alpha, \beta)$

By using below equation to find $O'(\alpha, \beta)$, 

$\Rightarrow \dfrac{\alpha -(-8 )}{4} = \dfrac{\beta -12}{7} = \dfrac {-2 (4(-8) + 7(12) +13)}{4^2 +7^2} $

$\Rightarrow \dfrac{\alpha -(-8 )}{4} = \dfrac{\beta -12}{7} = -2$

$\Rightarrow \alpha = -16, \beta = -2$

Hence new center $O'$ is $O'(-16,-2)$

The equation of the image of the circle through the mirror will be,

$\Rightarrow (x+16)^2 + (y +2)^2 = (5)^2$

$\Rightarrow x^2 +y^2 + 32x +4y + 235$

So correct option is $D$

The image of the pair of lines represented by $\displaystyle  3x^{2}+4xy+5y^{2}=0 $ in the line mirror x = 0 is

  1. $\displaystyle 3x^{2}-4xy+5y^{2}=0 $

  2. $\displaystyle 3x^{2}-4xy-5y^{2}=0 $

  3. $\displaystyle 5y^{2}-4xy-3x^{2}=0 $

  4. none of these


Correct Option: A
Explanation:
Given pair
$3x^2+4xy+5y^2=0$
$x=0$ is the $Y-axis $ hence the $x$-coordinates will become $-x$ and $y$-coordinates remains same 
Hence 
$3(-x)^2+4(-x)y+5y^2=0$
$3x^2-4xy+5y^2=0$

Let $0<\alpha< \dfrac{\pi}{4}$ be a fixed angle. If $\mathrm{P}=(\cos\theta,\sin\theta)$ and $\mathrm{Q}=(\cos(\alpha-\theta),\sin(\alpha-\theta))$ then $\mathrm{Q}$ is obtained from $\mathrm{P}$ by :

  1. clockwise rotation around the origin through an angle $\alpha$

  2. anticlockwise rotation around the origin through an angle $\alpha$

  3. reflection in the line through origin with slope $\tan\alpha$

  4. reflection in the line through origin with slope $\displaystyle \tan\frac{\alpha}{2}$


Correct Option: D
Explanation:
$P =\left(\cos \theta, \sin \theta\right)$ ; $Q=\left(\cos \left(\alpha -\theta \right),\sin \left(\alpha -\theta \right)\right)$

Angle between $P$ and $Q$ is $\tan^{-1}$  $\left(\dfrac{\sin\left(\alpha -\theta \right)-\sin\alpha }{\cos\left(\alpha -\theta \right)-\cos\alpha }  \right)$

$=\tan^{-1}\left( \tan \alpha  \right)=\alpha $

$\therefore$ mid point of $P$ and $Q$ is $ \left(\dfrac{\cos\theta + \cos(\alpha -\theta)}{2}, \dfrac{\sin\theta +\sin( \alpha -\theta)}{2}\right)$

$= \left(  \cos\dfrac{\alpha }{2} \cos\left(\dfrac{\theta-\alpha }{2}\right), \sin\dfrac{\alpha }{2}\cos\left(\dfrac{\theta-\alpha }{2}\right) \right)$

$= \cos\left(\dfrac {\theta -\alpha }{2}\right)\left( \cos\dfrac{\alpha }{2},\sin\dfrac{\alpha }{2} \right)$

Which is a point on line with slope $y=\tan\dfrac{\alpha }{2}$

$\therefore$ $Q$ is obtained by reflection of origin with slope $\tan$ $\dfrac{\alpha }{2}$.
Hence, option 'D' is correct.


The point $(4, 1)$ undergoes the following three transformations successively
i) Reflection about the line $\mathrm{y}=\mathrm{x}$
ii) Transformation through a distance of $2$ units along the $+\mathrm{v}\mathrm{e}$ direction of the x-axis
iii) Rotation through an angle $\displaystyle \frac{\pi}{4}$ about the origin in the anticlockwise direction. The final position of the point is given by the co-ordinates 

  1. $\left(\displaystyle \frac{-1}{\sqrt{2}}\frac{7}{\sqrt{2}}\right)$

  2. $(-2,7\sqrt{2})$

  3. $\left(\displaystyle \frac{7}{\sqrt{2}}\frac{1}{\sqrt{2}}\right)$

  4. $(7, 1)$


Correct Option: C
Explanation:

Under the transformation reflection about $y = x$ the new point is $(1,4)$
Under the transformation of shifting it $+2$ units along x-axis the new point is $(1+2,4) = (3,4)$
Under the transformation of rotation of $\dfrac{\pi}{4}$
$y= -X \sin  \theta +y\cos\ \theta$

$X=\dfrac{3}{\sqrt{2}}+\dfrac{4}{\sqrt{2}}=\dfrac{7}{\sqrt{2}}$

$y=\dfrac{3}{\sqrt{2}}+\dfrac{4}{\sqrt{2}}=\dfrac{1}{\sqrt{2}}$

The image of the origin with reference to the line $4x + 3y - 25 = 0$, is

  1. $(-8, 6)$

  2. $(8, 6)$

  3. $(-3, 4)$

  4. $(8, -6)$


Correct Option: B
Explanation:

Let the image or (reflection) of the origin with reference to the line $4x + 3y - 25 = 0$ is $(h, k)$.
$\therefore \dfrac {h - 0}{4} = \dfrac {k - 0}{3} = \dfrac {-2(0 + 0 - 25)}{16 + 9} = \dfrac {50}{25} = 2$
$\therefore \dfrac {h}{4} = 2\Rightarrow h = 8$
and $\dfrac {k}{3} = 2\Rightarrow k = 6$
$\therefore$ The required point is $(8, 6)$.

A light ray gets reflected from the $ x= -2 $ .If the reflected ray touches the circle $ x^{2}+y^{2}=4 $ and point of incident is $(-2,-4)$,then equation of incident ray is

  1. $ 4y+3x+22=0 $

  2. $ 3y+4x+20=0 $

  3. $ 4y+2x+20=0 $

  4. $ y+x+6=0 $


Correct Option: A

The image of the point $(3, 8)$ with respect to the line $x + 3y = 7$ is

  1. $(-1, -4)$

  2. $(-1, 4)$

  3. $(1, -4)$

  4. $(1, 4)$


Correct Option: A
Explanation:

Image of any Point $(\alpha , \beta)$ with respect to line $ax+by +c = 0$ is given by equation,


$\Rightarrow \dfrac{x -\alpha}{a} = \dfrac{y - \beta}{b} = \dfrac{-2(a\alpha + b \beta + c )}{a^2 + b^2}$  ....$(1)$

Now the given point is $(3,8)$ and the given line is $x + 3y - 7 = 0$

Putting the values in equation  $(1)$, we get,

$\Rightarrow \dfrac{x -3}{1} = \dfrac{y - 8} {3} = \dfrac{ -2(1.3 + 3.8 -7 )}{1^2 + 3^2} = -4$

Hence $\Rightarrow x= -1$ and $y = -4$

Correct option is $A$.

 The point $(4, 1)$ undergoes the following three transformations successively
(a) Reflection about the line $y = x$

(b) Transformation through a distance $2$ units along the positive direction of the x-axis.

(c) Rotation through an angle $p/4$ about the origin in the anti clockwise direction.

The final position of the point is given by the co-ordinates

  1. $\left(\dfrac{4}{\sqrt{2}} , \dfrac{1}{\sqrt{2}}\right)$

  2. $\left(-\dfrac{1}{\sqrt 2} , \dfrac{7}{\sqrt 2}\right)$
  3. $\left(\dfrac{1}{\sqrt{2}} , \dfrac{7}{\sqrt{2}}\right)$

  4. $\left(-\dfrac{3}{\sqrt{2}} , \dfrac{4}{\sqrt{2}}\right)$

Correct Option: B
Explanation:

Given Point $P(4,1)$


$(a)$ Reflection of given point about the line $y=x$
In Point P $x=4$ Hence about the line y-coordinate be $y=x\Rightarrow y=4$
Point P become $P(1,4)$

$(b)$ Transformation of Point P through distance $2$ units along the positive direction of the x-axis
$P(1+2,4)\equiv P(3,4)$

$(c)$Rotation of Point P through angle $\dfrac{\pi}{4}$ about origin in anti clockwise direction
$P\left (  r\cos\left ( \alpha+\dfrac{\pi}{4} \right ),r\sin\left ( \alpha+\dfrac{\pi}{4} \right )\right )$

Given point $P(3,4)$
$r=\sqrt{3^2+4^2}=5$
$\tan\alpha=\dfrac{4}{3}$
Hence In right angle triangle here hypotenuse be $5$
$\cos\alpha=\dfrac{3}{5}$ and $\sin\alpha=\dfrac{4}{5}$

$\cos\left ( \alpha+\dfrac{\pi}{4} \right )=\cos\alpha\cos\dfrac{\pi}{4}-\sin\alpha\sin\dfrac{\pi}{4}$

$\cos\left ( \alpha+\dfrac{\pi}{4} \right )=\dfrac{3}{5}\times \dfrac{1}{\sqrt{2}}-\dfrac{4}{5}\times \dfrac{1}{\sqrt{2}}=-\dfrac{1}{5\sqrt{2}}$

$r\cos\left ( \alpha+\dfrac{\pi}{4}\right )=5\times \dfrac{-1}{5\sqrt{2}}=-\dfrac{1}{\sqrt{2}}$

$\sin\left ( \alpha+\dfrac{\pi}{4} \right )=\sin\alpha\cos\dfrac{\pi}{4}+\cos\alpha\sin\dfrac{\pi}{4}$

$\sin\left ( \alpha+\dfrac{\pi}{4} \right )=\dfrac{4}{5}\times \dfrac{1}{\sqrt{2}}+\dfrac{3}{5}\times \dfrac{1}{\sqrt{2}}=\dfrac{7}{5\sqrt{2}}$

$r\sin\left ( \alpha+\dfrac{\pi}{4}\right )=5\times \dfrac{7}{5\sqrt{2}}=\dfrac{7}{\sqrt{2}}$


Point be 

$P\left (  -\dfrac{1}{\sqrt{2}},\dfrac{7}{\sqrt{2}}\right )$


Image of the point $\left( -8,12 \right) $ with respect to the line mirror $4x+7y+13=0$ is 

  1. $\left( 16,2 \right) $

  2. $\left( -16,-2 \right) $

  3. $\left( -12,5 \right) $

  4. $\left( 12,-5 \right) $


Correct Option: B
Explanation:

Here, $(x _1,y _1)$ is $(-8,12)$


Let $(\alpha,\beta)$ be image of the point.


$a=4,\,b=7$ and $c=13$

$\Rightarrow$  $\dfrac{\alpha+8}{4}=\dfrac{\beta-12}{7}=\dfrac{-2[4(-8)+7(12)+13]}{(4)^2+(7)^2}$

$\Rightarrow$  $\dfrac{\alpha+8}{4}=\dfrac{\beta-12}{7}=\dfrac{-2(-32+84+13)}{16+49}$

$\Rightarrow$  $\dfrac{\alpha+8}{4}=\dfrac{\beta-12}{7}=\dfrac{-2(65)}{65}$

$\Rightarrow$  $\dfrac{\alpha+8}{4}=\dfrac{\beta-12}{7}=-2$

$\Rightarrow$ $\dfrac{\alpha+8}{4}=-2$  and  $\dfrac{\beta-12}{7}=-2$

$\Rightarrow$  $\alpha+8=-8$   and  $\beta-12=-14$

$\Rightarrow$  $\alpha=-16$ and $\beta=-2$

So, the image of the point is $(-16,-2).$

Equation of line equidistant from lines $2x + 3y = 5$ and $4x + 6y = 11$ is

  1. $(x + y - 3)(x - y - 1) = 0$

  2. $8x + 12y = 1$

  3. $x - y = 2$

  4. None


Correct Option: B

A ray of light along $x+\sqrt{3}y=\sqrt{3}$ get reflected upon reaching x-axis, the equation of the reflected ray is?

  1. $y=x+\sqrt{3}$

  2. $\sqrt{3}y=x-\sqrt{3}$

  3. $y=\sqrt{3}x-\sqrt{3}$

  4. $\sqrt{3}y=x-1$


Correct Option: B

What is the reflection of the point $(6,-1)$ in the line $y=2$?

  1. $(-2,-1)$

  2. $(-6,5)$

  3. $(6,5)$

  4. $(2,1)$


Correct Option: C

The image of (2, -3) in the y - axis is

  1. (2, 3)

  2. (-2, 3)

  3. (-2, -3)

  4. (2, -3)


Correct Option: B

If ${ P } _{ 1 }\left( \dfrac { 1 }{ 5 } ,\alpha  \right)$ and ${P } _{ 2 }\left( \beta ,\dfrac { 18 }{ 5 }  \right)$ be the images of point $P\left( 1,\gamma  \right)$ about lines ${ L } _{ 1 }:2x-y=\lambda$ and ${ L } _{ 2 }:2y+x=4$ respectively, then the value of $\alpha$is-

  1. $-\dfrac { 3 }{ 5 }$

  2. $\dfrac { 2 }{ 5 }$

  3. $\dfrac { 7 }{ 5 }$

  4. $-\dfrac { 8 }{ 5 }$


Correct Option: A

The image of $P(a, b)$ in the line $y= -x$ is $Q$ and the image of $Q$ in the line $y=x$ is $R$. Then the midpoint of $PR$ is

  1. $(a+b, b+a)$

  2. $\left(\dfrac{a+b}{2}, \dfrac{b+a}{2}\right)$

  3. $(a-b, b-a)$

  4. $(0, 0)$


Correct Option: D
Explanation:

Consider point P and Q
The line which is perpendicular to $y=-x$ and passes through $(a,b)$ will be
$\dfrac{y-b}{x-a}=1$
$y=x-(a-b)$
Now the point where it intersects $y=-x$ is
$-x=x-(a-b)$
$2x=(a-b)$
$x=\dfrac{a-b}{2}$ and hence $y=\dfrac{b-a}{2}$
This will be the mid point of PQ since Q is the image of point P on the line $y=-x$
Therefore $Q=(-b,-a)$
Similarly $R=(-a,-b)$
Hence The midpoint of PR will be $(0,0)$

If $\displaystyle \left ( -2, 6 \right )$ is the image of the point $\displaystyle \left ( 4,2 \right )$ with respect to the line $\displaystyle L=0$, then $\displaystyle L=$

  1. $\displaystyle 6x-4y-7=0$

  2. $\displaystyle 2x-3y-5=0$

  3. $\displaystyle 3x-2y+5=0$

  4. $\displaystyle 3x-2y+10=0$


Correct Option: C
Explanation:

Slope of line joining the image $Q(-2,6)$ and the point $P(4,2)$ is $\displaystyle -\frac{2}{3}$

So, the slope of mirror $L$ is $\displaystyle \frac{3}{2}$

Mid-point of $PQ$ is $(1,4)$

Since, the image and point are equidistant from mirror. So, this point $(1,4)$ lies on the mirror.

So, the equation of mirror is
$y-4=\displaystyle \frac{3}{2} (x-1)$

$\Rightarrow 3x-2y+5=0$

The equation of image of pair of lines $y=|x-1|$ with respect to y-axis is 

  1. ${x^2} - {y^2} - 2x + 1 = 0$

  2. ${x^2} - {y^2} - 4x + 4 = 0$

  3. $4{x^2} - 4x - {y^2} + 1 = 0$

  4. ${x^2} - {y^2} + 2x + 1 = 0$


Correct Option: D
Explanation:

We have $y=|x-1|$


$\Rightarrow y^2=(x-1)^2$

Change $x$ by $-x$, then the required image is 

$y^2=(-x-1)^2$

$\Rightarrow y^2=x^2+2x+1$

$\Rightarrow x^2-y^2+2x+1=0$

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