(PHP 4, PHP 5, PHP 7, PHP 8)
atan — Arc tangent
$num): float
Returns the arc tangent of num in radians.
atan() is the inverse function of
tan(), which means that
a==tan(atan(a)) for every value of a that is within
atan()'s range.
numThe argument to process
The arc tangent of num in radians.