# ACOS

### In this article

Returns the arccosine, or inverse cosine, 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 pi.

## Syntax

```
ACOS(number)
```

#### Parameters

Term | Definition |
---|---|

Number | The cosine of the angle you want and must be from -1 to 1. |

## Return value

Returns the arccosine, or inverse cosine, of a number.

## Remarks

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

## Example

Formula | Description | Result |
---|---|---|

=ACOS(-0.5) | Arccosine of -0.5 in radians, 2*pi/3. | 2.094395102 |

=ACOS(-0.5)*180/PI() | Arccosine of -0.5 in degrees. | 120 |