acos

(PHP 4, PHP 5, PHP 7, PHP 8)

acos — Arc cosine

Description

acos(float $num): float

Returns the arc cosine of num in radians. acos() is the inverse function of cos(), which means that $num == cos(acos($num)) for every value of num that is in the domain of acos().

Parameters

num: The argument to process

Return Values

The arc cosine of num in radians.

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User Contributed Notes 1 note

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isweet479338 at gmail dot com ¶

6 days ago

Parameter:
$num: A float value between -1 and 1. (Outside this range will return NAN)

Returns:
The arc cosine of the number in radians.

NAN (Not A Number) if the input is outside [-1, 1].

<?php
$cosValue = 0.5;
$angle = acos($cosValue); // returns angle in radians
echo $angle; // 1.0471975512 (which is ~60 degrees)

echo rad2deg($angle); // Convert to degrees: ~60
?>