Please answer the following question: Extract the answer to the question from the following context. Question: According to Han, what is math? Context: Three Han mathematical treatises still exist. These are the Book on Numbers and Computation, the Arithmetical Classic of the Gnomon and the Circular Paths of Heaven and the Nine Chapters on the Mathematical Art. Han-era mathematical achievements include solving problems with right-angle triangles, square roots, cube roots, and matrix methods, finding more accurate approximations for pi, providing mathematical proof of the Pythagorean theorem, use of the decimal fraction, Gaussian elimination to solve linear equations, and continued fractions to find the roots of equations.
Answer:
Art