This calculates the 3rd side of an imaginary triangles length using the Pythagorean Theorem to calculate it. The Pythagorean theorem is used to find the length of the of a side of a right triangle. In a right triangle, the sum of the squares of the lengths of the legs of a triangle is equal to the squares of the length of the hypotenuse. Here is the code in python: import math print("Side 1?") side1 = float(input()) s1sq = side1 * side1 print("Side 2?") side2 = float(input()) s2sq = side2 * side2 s3sq = s1sq + s2sq print("Side 3 equals:") side3 = math.sqrt(s3sq) print(side3) Thanks the big fat notebook series made by the creators of brain quest. And myself for using my brain.