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 ALSOatan2(3M), isnan(3M), math.h(3HEAD), tan(3M), attributes(5), stan‐
dards(5)SunOS 5.10 12 Jul 2006 atan(3M)