Brahmagupta was an Indian mathematician and astronomer who lived in the 6th century CE. He is known for his work on the geometry of triangles, including his discovery of Brahmagupta's formula for the area of a cyclic quadrilateral.

Brahmagupta's formula for the area of a cyclic quadrilateral is given by $$A = \sqrt{(s - a)(s - b)(s - c)(s - d)}$$, where $$s$$ is the semiperimeter of the quadrilateral and $$a, b, c, d$$ are the lengths of its sides.

Baudhayana is considered to be the father of Indian geometry. He lived in the 8th century BCE and is known for his work on the Sulba Sutras, a collection of mathematical texts that deal with topics such as geometry, algebra, and astronomy.

Brahmagupta's theorem states that the sum of the squares of the diagonals of a cyclic quadrilateral is equal to the sum of the squares of its sides. This theorem is also known as Brahmagupta's quadrilateral theorem.

Aryabhata was an Indian mathematician and astronomer who lived in the 5th century CE. He is known for his work on the geometry of circles, including his discovery of the formula for the area of a circle.

Aryabhata's formula for the area of a circle is given by $$A = \pi r^2$$, where $$r$$ is the radius of the circle.

Bhaskara II was an Indian mathematician and astronomer who lived in the 12th century CE. He is known for his work on the geometry of spheres, including his discovery of the formula for the volume of a sphere.

Bhaskara II's formula for the volume of a sphere is given by $$V = \frac{4}{3}\pi r^3$$, where $$r$$ is the radius of the sphere.

Varahamihira was an Indian mathematician and astronomer who lived in the 6th century CE. He is known for his work on the geometry of polyhedra, including his discovery of the formula for the volume of a pyramid.

Varahamihira's formula for the volume of a pyramid is given by $$V = \frac{1}{3}Bh$$, where $$B$$ is the area of the base of the pyramid and $$h$$ is its height.

Aryabhata was an Indian mathematician and astronomer who lived in the 5th century CE. He is known for his work on the geometry of curves, including his discovery of the formula for the area of a parabola.

Aryabhata's formula for the area of a parabola is given by $$A = \frac{1}{2}bh$$, where $$b$$ is the length of the base of the parabola and $$h$$ is its height.

None of the Indian mathematicians mentioned in the options are known for their work on the geometry of fractals.

None of the Indian mathematicians mentioned in the options are known for their work on the geometry of topology.

None of the Indian mathematicians mentioned in the options are known for their work on the geometry of differential geometry.