The acos() function returns the arc cosine of a number.
float acos ( float $arg )
Returns the arc cosine of arg in radians. acos() is the complementary function of cos(), which means that a==cos(acos(a)) for every value of a that is within acos()' range.
| Parameter | Description |
|---|---|
| arg | The argument to process |
The arc cosine of arg in radians.