acos()
acos() — Arc cosine.
Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.
What it does
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().
Signature
acos(float $num): float
Parameters
| Parameter | Type | What it takes |
|---|---|---|
| $num | float | The argument to process |
Return value
The arc cosine of num in radians.
Example
The PHP manual ships no example for acos(); the signature and the parameter table above are the contract.
See also
cos(), acosh(), asin(), atan()
All PHP 8.5 built-in functions
Reference card built from the PHP manual page acos() (PHP documentation, CC BY 3.0). The page is generated from the manual, so the wording of the parameter and return value text follows php.net.