Brahmagupta, an Indian mathematician and astronomer who lived in the 7th century CE, is widely regarded as the first mathematician to develop the concept of zero and use it in mathematical operations.

Aryabhatiya is a seminal mathematical treatise written by Aryabhata in the 5th century CE. It covers a wide range of topics, including arithmetic, algebra, trigonometry, and astronomy.

Bhaskara II, an Indian mathematician who lived in the 12th century CE, is credited with discovering the Fibonacci sequence and providing a recursive formula for it.

Nicomachus's Theorem, also known as the Sum of Squares Theorem, states that the sum of the squares of the first n natural numbers is equal to n(n+1)(2n+1)/6.

Aryabhata is credited with developing the concept of the sine function and providing a table of sine values.

Lilavati is a mathematical treatise written by Bhaskara II in the 12th century CE. It covers a wide range of topics, including arithmetic, algebra, geometry, and astronomy.

Brahmagupta is credited with developing the theory of continued fractions, which is a method for representing a rational number as an infinite series of fractions.

Hero's Formula states that the area of a triangle is equal to half the product of its base and height.

Aryabhata is credited with developing the concept of the decimal system, which is now used worldwide.

Srinivasa Ramanujan did not write any mathematical treatises. He communicated his mathematical discoveries through letters and collaborations with other mathematicians.

Srinivasa Ramanujan is known for his groundbreaking work on the theory of modular forms, which has applications in number theory, analysis, and physics.

The Angle Sum Theorem states that the sum of the angles of a triangle is equal to 180 degrees.

Brahmagupta is credited with developing the concept of the negative number and providing rules for performing operations with negative numbers.

Surya Siddhanta is a mathematical and astronomical treatise written by Suryadeva Yajvan in the 12th century CE. It covers a wide range of topics, including astronomy, trigonometry, and astrology.

Srinivasa Ramanujan is known for his groundbreaking work on the theory of elliptic functions, which has applications in number theory, analysis, and physics.