# ACOS

Returns the arccosine of a number. The arccosine is the angle whose cosine is number. The returned angle is given in radians in the range 0 (zero) to p (pi).

**Syntax**

**ACOS**(**number**)

**Number** is the cosine of the angle you want and must be from -1 to 1.

If you want to convert the result from radians to degrees, multiply it by 180/PI().

**Examples**

`ACOS(-0.5)`

equals 2.094395 (2p/3 radians)

`ACOS(-0.5)*180/PI()`

equals 120 (degrees)