Explanation:
You are probably familiar with the formula [tex]a^2+b^2 = c^2[/tex] which is the pythagorean theorem.
The [tex]a^2[/tex] is the square of the first leg 'a', while [tex]b^2[/tex] is the square of the second leg b. Adding those two squares leads to the square of the hypotenuse c, aka [tex]c^2[/tex]. This only works with right triangles, which are triangles that have a 90 degree angle.