# ACOS

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