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 ALSO
atan(3M), isnan(3M), math.h(3HEAD)tan(3M), attributes(5), standards(5)
SunOS 5.11 12 Jul 2006 atan2(3M)
