The hypotenuse of a right triangle is a special kind of line, as it is always the longest side and it bisects the right angle formed by the other two sides. This kind of triangle is the most commonly used in mathematics and geometry and the hypotenuse can be used to calculate the lengths of the other sides. While the length of the hypotenuse is not always known, there are ways to determine it. For example, the Pythagorean Theorem states that a²+b²=c², where c is the length of the hypotenuse. This can be used to solve any right triangle, giving the lengths of all three sides. Aside from the Pythagorean Theorem, there are various other trigonometric and other mathematical formulas for finding the hypotenuse. The hypotenuse of a right triangle is also used in various common activities. For example, engineers use it to calculate the inverse of a triangle, in which the length of one side is used to estimate the sizes of the other two sides. Surveyors also use the hypotenuse to measure distances, as well as to calculate the area of a triangle. All of these applications and more are based on the special properties of the hypotenuse.