# Documentation/How Tos/Calc: ACOS function

From Apache OpenOffice Wiki

## ACOS

Returns the inverse cosine (the arccosine) of a number.

### Syntax:

**ACOS(number)**

- returns the inverse trigonometric cosine of
, in other words the angle (in radians) whose cosine is**number**. The angle returned is between**number**and**0**.**PI**

- To return the angle in degrees, use the
function.**DEGREES**

### Example:

**ACOS(-1)**

- returns
(**3.14159265358979**radians).**PI**

**DEGREES(ACOS(0.5))**

- returns
. The cosine of**60**degrees is**60**.**0.5**