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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 |