Understanding PHP’s atan() Function: Usage, Parameters, and Examples

Function Overview

atan() returns the inverse tangent (arctangent) of a numeric argument, expressed in radians. It is the mathematical inverse of tan(), satisfying a == tan(atan(a)) for values within the function’s principal range.

Signature

float atan(float $arg)

Parameter

$arg : The numeric value whose arctangent is to be computed.

Return Value

Floating‑point number representing the arctangent of $arg in radians.

Example

<?php
echo atan(0.50) . "
";
echo atan(-0.50) . "
";
echo atan(5) . "
";
echo atan(-5) . "
";
echo atan(100) . "
";
echo atan(-100) . "
";
?>

Sample Output

0.46364760900081
-0.46364760900081
1.373400766945
-1.373400766945
1.5607966601082
-1.5607966601082