Introduction to number theory lecture 44 Pythagorean triangles

This lecture is part of my Berkeley math 115 course "Introduction to number theory"
For the other lectures in the course see    • Introduction to number theory (Berkeley Ma...  

We apply the theory of binary quadratic forms to study pythagorean triangles with x^2 + y^2 = z^2

The textbook is "An introduction to the theory of numbers" by Niven, Zuckerman, and Montgomery (5th edition).