Synopsis
float atan2f(float x,
             float y);
Description

atan2f returns the value, in radians, of the inverse circular tangent of y divided by x using the signs of x and y to compute the quadrant of the return value. The principal value lies in the interval [??/2, +?] radians.

If x = y = 0, errno is set to EDOM and atan2f returns HUGE_VALF.

atan2f(x, NaN) is NaN.
atan2f(NaN, x) is NaN.
atan2f(±0, +(anything but NaN)) is ±0.
atan2f(±0, ?(anything but NaN)) is ±?.
atan2f(±(anything but 0 and NaN), 0) is ±?.
atan2f(±(anything but ∞ and NaN), +∞) is ±0.
atan2f(±(anything but ∞ and NaN), ?∞) is ±?.
atan2f(±∞, +∞) is ±?.
atan2f(±∞, ?∞) is ±?.
atan2f(±∞, (anything but 0, NaN, and ∞)) is ±?.