atan2, atan2f, atan2l - arc tangent function of two variables
#include <math.h>
double atan2(double y, double x);
float atan2f(float y, float x);
long double atan2l(long double y, long double x);
Link with -lm
.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
These functions calculate the principal value of the arc tangent of y/x
, using the signs of the two arguments to determine the quadrant of the result.
On success, these functions return the principal value of the arc tangent of y/x
in radians; the return value is in the range [-pi, pi].
If y
is +0 (-0) and x
is less than 0, +pi (-pi) is returned.
If y
is +0 (-0) and x
is greater than 0, +0 (-0) is returned.
If y
is less than 0 and x
is +0 or -0, -pi/2 is returned.
If y
is greater than 0 and x
is +0 or -0, pi/2 is returned.
x
or y
is NaN, a NaN is returned.
y
is +0 (-0) and x
is -0, +pi (-pi) is returned.
If y
is +0 (-0) and x
is +0, +0 (-0) is returned.
If y
is a finite value greater (less) than 0, and x
is negative infinity, +pi (-pi) is returned.
If y
is a finite value greater (less) than 0, and x
is positive infinity, +0 (-0) is returned.
If y
is positive infinity (negative infinity), and x
is finite, pi/2 (-pi/2) is returned.
If y
is positive infinity (negative infinity) and x
is negative infinity, +3*pi/4 (-3*pi/4) is returned.
If y
is positive infinity (negative infinity) and x
is positive infinity, +pi/4 (-pi/4) is returned.