If y = f(x) and a function can be found so that x = g(y), then g(y) is said to be the inverse function of f(x). If y is a trigonometrical function of the angle x, say y = sinx, then x is the inverse trigonometrical function of y, written x = arcsiny or sin−1y. Similarly, the other trigonometrical functions form the inverse trigonometrical functions cos−1y, tan−1y, cot−1y, sec−1y, and cosec−1y. Inverse hyperbolic functions are also formed in this way, e.g. arcsinhy or sinh−1y, cosh−1y, and tanh−1y.