ref: 1f80d31f41a630860d1e1b5712546a3dc9993b4c
dir: /sys/src/libc/port/atan2.c/
#include <u.h>
#include <libc.h>
/*
atan2 discovers what quadrant the angle
is in and calls atan.
*/
double
atan2(double arg1, double arg2)
{
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;
}