(PHP 4, PHP 5, PHP 7, PHP 8)
acos — Arc cosine
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().
num
The argument to process
The arc cosine of num
in radians.