[alainbryden]

Oh and about the C² = A² + B², this is how it was proven by pythagorus:
Take your right angle triangle. It has three sides, A, B, and C
Use the classic 3, 4, 5 example so that it's easier.
Now what's the are of a a square? 2 times the side, or, the side² right?
If you make a square on each side of triangle, both of the smaller ones, broken down into single unit components, will fit into the second one.
I guess this can only be seen as a visual demonstration or coincidence of the law, but you can't actually prove it until you start learning all your other stuff like dealing in radians and solving using trigonometric equations which all comes back to the famous and ever usefull PI.