atanh

atan

#include <math.h>float atanf(float arg);double atan(double arg); long double atanl(long double arg);

atanf( ) and atanl( ) were added by C99.

The atan( ) family of functions returns the arc tangent of arg.

Related functions are asin( ), acos( ), atan2( ), tan( ), cos( ), sin( ), sinh( ), cosh( ), and tanh( ).