atan, atanf, atanl − arc tangent function

#include <math.h>

double atan(double x);

float atanf(float x);

long double atanl( long double x);

The atan() function calculates the arc tangent of x; that is the value whose tangent is x.

The atan() function returns the arc tangent in radians and the value is mathematically defined to be between -PI/2 and PI/2 (inclusive).

SVID 3, POSIX, BSD 4.3, ISO 9899. The float and long double variants are C99 requirements.

acos(3), asin(3), atan2(3), cos(3), sin(3), tan(3)