atan(3M) Mathematical Library Functions atan(3M)
NAME
atan, atanf, atanl - arc tangent function
SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double atan(double x);
float atanf(float x);
long double atanl(long double x);
DESCRIPTION
These functions compute the principal value of the arc tangent of x.
RETURN VALUES
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.
ERRORS
No errors are defined.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO
atan2(3M), isnan(3M), math.h(3HEAD), tan(3M), attributes(5), standards(5)
SunOS 5.11 12 Jul 2006 atan(3M)