atan2(3M) Mathematical Library Functions atan2(3M)NAME
atan2, atan2f, atan2l - arc tangent function
SYNOPSIS
c99 [ flag... ] file... -lm [ library... ]
#include <math.h>
double atan2(double y, double x);
float atan2f(float y, float x);
long double atan2l(long double y, long double x);
DESCRIPTION
These functions compute the principal value of the arc tangent of y/x,
using the signs of both arguments to determine the quadrant of the
return value.
RETURN VALUES
Upon successful completion, these functions return the arc tangent of
y/x in the range [ −pi,pi ] radians.
If y is ±0 and x is < 0, ±pi is returned.
If y is ±0 and x is > 0, ±0 is returned.
If y is < 0 and x is ±0, −pi/2 is returned.
If y is > 0 and x is ±0, pi/2 is returned.
If x is 0, a pole error does not occur.
If either x or y is NaN, a NaN is returned.
If y is ±0 and x is -0, ±pi is returned.
If y is ±0 and x is +0, ±0 is returned.
For finite values of ±y > 0, if x is −Inf, ±pi is returned.
For finite values of ±y > 0, if x is +Inf, ±0 is returned.
For finite values of x, if y is ±Inf, ±pi/2 is returned.
If y is ±Inf and x is −Inf, ±3pi/4 is returned.
If y is ±Inf and x is +Inf, ±pi/4 is returned.
If both arguments are 0, a domain error does not occur.
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 ALSOatan(3M), isnan(3M), math.h(3HEAD)tan(3M), attributes(5), standards(5)SunOS 5.10 12 Jul 2006 atan2(3M)