Pythagorean Theorem

Pie-thag-or-ian Thee-or-um

It's named after Pythagoras Of Samos, if you've never heard of him you should look him up sometime, he was a pretty cool dude.

But seriously, though, Google him sometime... :)

can only be used with right triangles, but even so it comes up a surprising amount. And it works every time, so that's cool.

*A perfect square is a number that when you square root 

( $\sqrt{x}$  ) it, you get a whole number