Brahmagupta is widely regarded as the father of Indian geometry due to his significant contributions to the field, including his work on the Pythagorean theorem, quadrilaterals, and cyclic quadrilaterals.

Brahmagupta's theorem is a fundamental result in geometry that establishes a relationship between the diagonals and sides of a cyclic quadrilateral.

Bhaskara II derived a formula for calculating the area of a triangle using its sides, known as Heron's formula, which is still widely used today.

The triangle sum theorem is a fundamental property of triangles that establishes the relationship between the angles of a triangle.

Aryabhata developed a method for constructing a regular polygon with a given number of sides using a geometric progression.

The triangle similarity theorem establishes a relationship between the areas and corresponding sides of similar triangles.

Aryabhata derived a formula for calculating the volume of a sphere, which is still widely used today.

The polygon interior angle sum theorem establishes a relationship between the number of sides of a polygon and the sum of its interior angles.

Bhaskara II developed a method for solving quadratic equations, which is known as the Bhaskara's method.

The circle area theorem establishes a relationship between the area of a circle and its radius.

Aryabhata derived a formula for calculating the circumference of a circle, which is still widely used today.

The Pythagorean theorem is a fundamental result in geometry that establishes a relationship between the sides of a right triangle.

Brahmagupta developed a method for constructing a regular heptagon using a geometric progression.

The cyclic quadrilateral angle sum theorem establishes a relationship between the opposite angles of a cyclic quadrilateral.

Bhaskara II developed a method for solving cubic equations, which is known as the Bhaskara's method.