ARCCOS is the arccosine trigonometric function. ARCCOS is also called the inverse cosine function. The ARCCOS function accepts a number between -1 and 1 inclusive and returns the angle from the range 0 through +pi that has that cosine.

The arccosine is calculated similarly to the arcsine function and uses the following identity:

ARCCOS(x)= pi/2 - ARCSIN(x)

The value of pi/2 is given under “Common Constants” later in this section.