PHP acos() Function

PHP Math Functions

Definition and Usage

The acos() function returns the inverse cosine of a number.

Syntax

acos(x)
Parameter Description
x Required. A number, ranging between -1 and 1.

Description

returns x inverse cosine value, in radians. acos() is cos() is the inverse function, which means that each value within the range of acos() is a==cos(acos(a)).

if x is outside the range of -1 to 1, then -1.#IND is returned. If it is -1, then the value of PI is returned.

Example

In this example, we will calculate the inverse cosine of different values:

<?php
echo(acos(0.64));
echo(acos(0));
echo(acos(-1));
echo(acos(1));
echo(acos(2));
?>

Output:

0.876298061168
1.57079632679
3.14159265359
0
-1.#IND

PHP Math Functions