1 files changed, 60 insertions, 0 deletions
diff --git a/src/lib/math/asin.go b/src/lib/math/asin.go
new file mode 100644
index 000000000..6297064db
--- /dev/null
+++ b/src/lib/math/asin.go
@@ -0,0 +1,60 @@
+// 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 asin
+
+import	sys "sys"
+import	atan "atan"
+import	sqrt "sqrt"
+export	asin, acos
+
+/*
+ * asin(arg) and acos(arg) return the arcsin, arccos,
+ * respectively of their arguments.
+ *
+ * Arctan is called after appropriate range reduction.
+ */
+
+const
+(
+	pio2	= .15707963267948966192313216e1;
+)
+
+func
+asin(arg double)double
+{
+	var temp, x double;
+	var sign bool;
+
+	sign = false;
+	x = arg;
+	if x < 0 {
+		x = -x;
+		sign = true;
+	}
+	if arg > 1 {
+		return sys.NaN();
+	}
+
+	temp = sqrt.sqrt(1 - x*x);
+	if x > 0.7 {
+		temp = pio2 - atan.atan(temp/x);
+	} else {
+		temp = atan.atan(x/temp);
+	}
+
+	if sign {
+		temp = -temp;
+	}
+	return temp;
+}
+
+func
+acos(arg double)double
+{
+	if(arg > 1 || arg < -1) {
+		return sys.NaN();
+	}
+	return pio2 - asin(arg);
+}