adjacent side	For a given acute angle in a right triangle, the adjacent side to that angle is the side that, along with the hypotenuse, forms that acute angle.
cofunctions	Two trigonometric functions, such as sine and cosine, for which the value of the first function at an acute angle equals the value of the second function at the complement of that angle.
cosine	If A is an acute angle of a right triangle, then the cosine of angle A is the ratio of the length of the side adjacent to angle A over the length of the hypotenuse.
hypotenuse	The side opposite the right angle in any right triangle. The hypotenuse is the longest side of any right triangle.
identity	An equation that is true for any possible value of the variable.
inverse function	If you take a function and reverse its inputs and outputs, then you get its inverse function.
opposite side	For a given acute angle in a right triangle, the opposite side to that angle is the side that is not one of the two sides that form that acute angle.
sine	If A is an acute angle of a right triangle, then the sine of angle A is the ratio of the length of the side opposite angle A over the length of the hypotenuse.
tangent	If A is an acute angle of a right triangle, then the tangent of angle A is the ratio of the length of the side opposite angle A over the length of the side adjacent to A.
trigonometric functions	A function of an angle expressed as the ratio of two of the sides of a right triangle that contains that angle; the sine, cosine, tangent, cotangent, secant, cosecant.