atan
(PHP 3, PHP 4 , PHP 5)
atan -- Arc tangent
Description
float
atan ( float arg )
Returns the arc tangent of arg in radians.
atan() is the complementary function of
tan(), which means that
a==tan(atan(a)) for every value of a that is within
atan()'s range.
See also:
atanh(),
asin(), and
acos().