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#include <math.h> double atan2(double y, double x); |
This function computes the angle, in the range [-Pi..Pi]
radians,
whose tangent is y/x
. In other words, it computes
the angle, in radians, of the vector (x,y) with respect to
the +x
axis, reckoning the counterclockwise direction as
positive, and returning the value in the range [-Pi, Pi]
.
The arc tangent, in radians, of y/x
. Pi
is
returned if x is negative and y is a negative zero,
-0.0
. -Pi
is returned, if x is negative, and
y is a positive zero, +0.0
.
If either x or y is infinite, atan2
returns,
respectively, Pi
with the sign of y or zero, and
errno
is left unchanged. However, if both arguments are
infinite, the return value is NaN
and errno
is set to
EDOM
.
A NaN
is returned, and errno
is set to EDOM
, if
either x and y are both zero, or if either one of the
arguments is a NaN
.
ANSI/ISO C | C89; C99 |
POSIX | 1003.2-1992; 1003.1-2001 |
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Copyright © 2004 by DJ Delorie | Updated Apr 2004 |