ATAN(3M) Mathematical Library Functions ATAN(3M)

atan, atanf, atanl - arc tangent function

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double atan(double x);

float atanf(float x);

long double atanl(long double x);

These functions compute the principal value of the arc tangent of x.

Upon successful completion, these functions return the arc tangent of x in the range [−pi/2,pi/2] radians.

If x is NaN, NaN is returned.

If x is ±0, x is returned.

If x is ±Inf, ±pi/2 is returned.

No errors are defined.

See attributes(7) for descriptions of the following attributes:

Interface Stability Standard
MT-Level MT-Safe

math.h(3HEAD), atan2(3M), isnan(3M), tan(3M), attributes(7), standards(7)

July 12, 2006 SunOS 5.11