| // Copyright 2009 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| package atan2 | |
| import atan "atan" | |
| export atan2 | |
| /* | |
| atan2 discovers what quadrant the angle | |
| is in and calls atan. | |
| */ | |
| const | |
| ( | |
| pio2 = .15707963267948966192313216e1; | |
| pi = .3141592653589793238462643383276e1; | |
| ) | |
| func | |
| atan2(arg1, arg2 double) double | |
| { | |
| var x double; | |
| if arg1+arg2 == arg1 { | |
| if arg1 >= 0 { | |
| return pio2; | |
| } | |
| return -pio2; | |
| } | |
| x = atan.atan(arg1/arg2); | |
| if arg2 < 0 { | |
| if x <= 0 { | |
| return x + pi; | |
| } | |
| return x - pi; | |
| } | |
| return x; | |
| } |