NAME

atan, atanf, atanl - arc tangent function

SYNOPSIS

#include <math.h>

double atan(double x);

float atanf(float x);

long double atanl( long double x);

Link with -lm.

DESCRIPTION

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

RETURN VALUE

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

CONFORMING TO

SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double variants are C99 requirements.

SEE ALSO

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