Given the following passage  "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 the following question. Note that the answer is present within the text.  Question: What type of geometrical shape did Pythagorean theorem address?
The answer to this question is:
right-angle triangles