===== Syntax =====

<code php>
float acos(float $val)
</code>

//(PHP 4 >= 4.07, PHP 5)//

^ $val | Value to compute the arc cosine for. |
^ RETURNS | Computes the trigonometry function ''inverse hyperbolic cosine'' for the degree in radians (**$val**). |

===== What it Does =====

This function computes the inverse hyperbolic cosine for the argument **$val** which is the degree in radians.

**Note: This function is not currently available for PHP on Windows.**

===== Example =====

<code php>
// compute the inverse hyperbolic cosine for 1.4 radians
echo 'acosh(1.4) = ' . acos(1.4);
</code>