1.7 atan, atanf—arc tangent

Synopsis

#include <math.h>
double atan(double x);
float atanf(float x);

Description

atan computes the inverse tangent (arc tangent) of the input value.

atanf is identical to atan, save that it operates on floats.

Returns
atan returns a value in radians, in the range of -pi/2 to pi/2.

Portability
atan is ANSI C. atanf is an extension.