Arccos Calculator

Arccos is the inverse of cosine: it takes a number and returns the angle whose cosine is that number. Enter a value from -1 to 1 and you get the angle in degrees, in radians, as a multiple of pi, in gradians and split into degrees, minutes and seconds. A second mode takes the adjacent side and the hypotenuse of a right triangle and works out the angle between them. Values outside -1 to 1 have no inverse cosine at all, so they are refused with an explanation rather than handed back as an error code.