What is the hypotenuse of a right triangle with legs of lengths 5 and 12?

The hypotenuse of a right triangle is the square root of the sums of the squares of the lengths of the other two sides, i.e. it is c, where c2 = (a2 + b2).

The hypotenuse for the example is c = [sqrt (52 + 122)] = [sqrt (25+144)]= sqrt [169] = 13.