ref: dfb4b522830edab8f3856289d326d6cf5e930644
dir: /sys/src/ape/lib/ap/math/atan2.c/
#include <math.h> #include <errno.h> /* atan2 discovers what quadrant the angle is in and calls atan. */ #define pio2 1.5707963267948966192313217 #define pi 3.1415926535897932384626434; double atan2(double arg1, double arg2) { if(arg1 == 0.0 && arg2 == 0.0){ errno = EDOM; return 0.0; } if(arg1+arg2 == arg1) { if(arg1 >= 0) return pio2; return -pio2; } arg1 = atan(arg1/arg2); if(arg2 < 0) { if(arg1 <= 0) return arg1 + pi; return arg1 - pi; } return arg1; }