# acos, acosh

## Purpose

Inverse cosine and inverse hyperbolic cosine.

## Synopsis

    Y = acos(X)
    Y = acosh(X)

## Description

`acos` and `acosh` operate element-wise on matrices. Their domains and ranges include complex values. All angles are in radians.

`acos(X)` returns the inverse cosine for each element of `X`. For real elements of `X` in the range [-1,1], `acos(X)` is real and in the range [0,`pi`]. For real elements of `X` outside the range [-1,1], `acos(X)` has nonzero imaginary parts.

`acosh(X)` returns the inverse hyperbolic cosine for each element of `X`.

## Examples

Graph the inverse cosine function for the range `-1 <= x <= 1`.

    x = -1:.05:1;
    plot(x, acos(x))

## Algorithm

## See Also

    atan2, cos, exp, funm, log, sin, sqrt, tan

(c) Copyright 1994 by The MathWorks, Inc.