A Pythagorean triple consists of three positive integers a, b, and c, such that a<sup>2</sup> + b<sup>2</sup> = c<sup>2</sup>. Such a triple is commonly written (a, b, c), and a well-known example is (3, 4, 5). If (a, b, c) is a Pythagorean triple, then so is (ka, kb, kc) for any positive integer k. A primitive Pythagorean triple is one in which a, b and c are coprime (that is, they have no common divisor larger than 1). A triangle whose sides form a Pythagorean triple is called a Pythagorean triangle, and is necessarily a right triangle.
Questions on basic geometry and Pythagorean geometry are on most high school tests