The equation "a2 + b2 = c2" refers to the Pythagorean theorem. With this theorem, it is possible to find the length of any side of a right triangle when given the length of the other two sides.
The Pythagorean theorem states the sum of the squares of the two legs of a right triangle is equal to the square of the hypotenuse. In this equation, the twos after each term are not indicators of multiplication by two but of squaring each term. Normally, mathematicians write them as superscripts above the regular line of the text. This formula provides the basis for the distance formula, which is useful in determining the distance between two points on a graph when given their coordinates.