## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$11^2+60^2=61^2$
According to the Pythagorean theorem, in a right-angled triangle, the sum of the square of the lengths of the shorter sides is equal to the square of the longest side, the hypotenuse. $61^2=3721$ $11^2+60^2=121 + 3600=3721$ Therefore, the triangle whose sides are of lengths 11, 60, and 61 is a right triangle.