Answer:
Pythagorean Theorem: A² + B² = C²
You would use it to find a missing side or missing hypotenuse of a right triangle by pluggin in all of the known values of the triangle into the equation and then solving it.
Explanation:
C² is the hypotenuse of the triangle (the longest side, and the side that is opposite the right angle).
A² and B² are the remaining two sides.