Explanation:
a² + b² = c²
think of it as leg1² + leg2² = hypotenuse²
so for example, you are given a triangle with leg1 5cm and leg2 2cm, what is the hypotenuse?
you would plug it into the formula as
5² + 2² = C²
then square the leg values
25 + 4 = c²
and then solve for c
29 = c²
then square root both sides
and the square root of 29 is 5.39
since this is just an example I created, you would most likely not be given a problem like this by your teacher, you would most likely get a whole number. Also the pythagorean theorem is only used with right triangles.
I hope this helped