# Reference/acos

From Kx Wiki

## Contents |

## acos (arc cosine function)

The `acos` function computes the arc cosine of its argument; that is the value whose cosine is the given argument. The result is in radians and lies between 0 and PI (the range is approximate due to rounding errors).

Null is returned if the argument is not between -1 and 1.

## Syntax

q)a:acos 0.5

## Example

q)acos -0.4 1.982313

## See also

For a complete list of functions, see the kdb+ Function Reference.