You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Han_dynasty

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.

Question:
During what era was the Nine Chapters on the Mathematical Art from?

Han