00:01
So let's suppose we have a triangle, a, b, c, and it has side lengths x, y, and z.
00:09
So our goal is to prove that if x squared plus y squared equals z squared, then a, b, c is a right triangle.
00:17
So let's suppose, for the sake of contradiction, that x squared plus y squared does equal z squared, but a b c is not a right triangle.
00:44
Now let's suppose that we can make a new triangle, pqr, that is a right triangle.
00:57
And we can make the legs whatever we like.
01:01
So first let's write this.
01:08
Suppose pqr is a right triangle.
01:17
And let's make the legs equal x and y...