Pythagorean Proofs

Watch the following video to help prove
Pythagoras's Theorey.
https://youtu.be/ANR4g0lPrEQ

Or search for other simple proofs online.

Isosceles and Equilateral Triangles and Pythagoros

Finding a sides of Isosceles and equilateral Triangles.

http://sites.csn.edu/istewart/Math120/Geometry/triangles.html

and watch the following video:
https://youtu.be/jAS1BgwhycE