In geometry, the term "hypotenuse" refers to the side of a right triangle that is opposite the right angle, which is also the longest side. Geometric and trigonometric problems typically use the hypotenuse in the Pythagorean Theorem.
Based on the Pythagorean Theorem, the hypotenuse can be defined as c = sqrt(a^2 + b^2), where c equals the length of the hypotenuse and a and b equal the lengths of the other two sides of a right triangle. The hypotenuse is also used in the trigonometric functions sine and cosine to find a ratio between the length of the hypotenuse and the length of one other side of the triangle. The word hypotenuse comes from a Latin term meaning "length under."