Answer:
The Pythagorean theorem is a proof that in any right triangle, if you square both of the lengths of the legs and add them (A^2+B^2) it will always equal the length of the hypotenuse squared (C^2).
Lets say you have a right triangle with the lengths of the legs being 3 and 4 and you need to find the hypotenuse with side length c. well 3^2+4^2=c^2 so
9+16=c^2, thus c^2 =25 and c=5.
