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PHP acos() Function

❮ PHP Math Reference

Example

Return the arc cosine of different numbers:

<?php
echo(acos(0.64) . "<br>");
echo(acos(-0.4) . "<br>");
echo(acos(0) . "<br>");
echo(acos(-1) . "<br>");
echo(acos(1) . "<br>");
echo(acos(2));
?>
Try it Yourself »

Definition and Usage

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

Tip: acos(-1) returns the value of Pi.


Syntax

acos(number);

Parameter Values

Parameter Description
number Required. Specifies a number in range -1 to 1

Technical Details

Return Value: The arc cosine of a number. Returns NAN if number is not in the range -1 to 1
Return Type: Float
PHP Version: 4+

❮ PHP Math Reference