1 files changed, 24 insertions, 0 deletions
diff --git a/src/base/math/atan2.c b/src/base/math/atan2.c
new file mode 100644
index 0000000..a681a80
--- /dev/null
+++ b/src/base/math/atan2.c
@@ -0,0 +1,24 @@
+#include <u.h>
+#include <base.h>
+/*
+	atan2 discovers what quadrant the angle
+	is in and calls atan.
+*/
+
+double
+math·atan2(double arg1, double arg2)
+{
+
+	if(arg1+arg2 == arg1) {
+		if(arg1 >= 0)
+			return math·PIO2;
+		return -math·PIO2;
+	}
+	arg1 = math·atan(arg1/arg2);
+	if(arg2 < 0) {
+		if(arg1 <= 0)
+			return arg1 + math·PI;
+		return arg1 - math·PI;
+	}
+	return arg1;
+}