1 files changed, 30 insertions, 0 deletions
diff --git a/src/pkg/math/tanh.go b/src/pkg/math/tanh.go
new file mode 100644
index 000000000..18d38ae8f
--- /dev/null
+++ b/src/pkg/math/tanh.go
@@ -0,0 +1,30 @@
+// 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 math
+
+import "math"
+
+/*
+ *	tanh(x) computes the hyperbolic tangent of its floating
+ *	point argument.
+ *
+ *	sinh and cosh are called except for large arguments, which
+ *	would cause overflow improperly.
+ */
+
+// Tanh computes the hyperbolic tangent of x.
+func Tanh(x float64) float64 {
+	if x < 0 {
+		x = -x;
+		if x > 21 {
+			return -1;
+		}
+		return -Sinh(x)/Cosh(x);
+	}
+	if x > 21 {
+		return 1;
+	}
+	return Sinh(x)/Cosh(x);
+}