MATLAB Function Reference |

**Syntax**

**Description**

```
Y = acos(X)
```

returns the inverse cosine (arccosine) for each element of `X`

. For real elements of `X`

in the domain , `acos(X)`

is real and in the range . For real elements of `X`

outside the domain , `acos(X)`

is complex.

The `acos`

function operates element-wise on arrays. The function's domains and ranges include complex values. All angles are in radians.

**Examples**

Graph the inverse cosine function over the domain .

**Definition**

The inverse cosine can be defined as

**Algorithm**

`acos`

uses FDLIBM, which was developed at SunSoft, a Sun Microsystems, Inc. business, by Kwok C. Ng, and others. For information about FDLIBM, see http://www.netlib.org.

**See Also**

abs | acosh |