Bhaskara II completes the Siddhanta Shiromani ('Crown of Treatises') at age 36, a work of 1,450 Sanskrit verses divided into four parts: Lilavati (arithmetic), Bijaganita (algebra), Grahaganita (planetary mathematics), and Goladhyaya (the sphere). The Bijaganita is the first text to recognize that every positive number has two square roots (positive and negative) and systematizes the chakravala method for solving Pell equations (Nx² + 1 = y²) centuries before Fermat. In the Siddhanta Shiromani he introduces results on derivatives of trigonometric functions anticipating differential calculus — the interpretation as a precursor of Newton/Leibniz is valid with caveats. MacTutor states that he 'achieved an understanding of the number system and the solution of equations which was not to be achieved in Europe for several centuries.'