diff --git a/src/pkg/math/asinh.go b/src/pkg/math/asinh.go
new file mode 100644
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+// Copyright 2010 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
+
+
+// The original C code, the long comment, and the constants
+// below are from FreeBSD's /usr/src/lib/msun/src/s_asinh.c
+// and came with this notice.  The go code is a simplified
+// version of the original C.
+//
+// ====================================================
+// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+//
+// Developed at SunPro, a Sun Microsystems, Inc. business.
+// Permission to use, copy, modify, and distribute this
+// software is freely granted, provided that this notice
+// is preserved.
+// ====================================================
+//
+//
+// asinh(x)
+// Method :
+//	Based on
+//	        asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
+//	we have
+//	asinh(x) := x  if  1+x*x=1,
+//	         := sign(x)*(log(x)+ln2)) for large |x|, else
+//	         := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
+//	         := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
+//
+
+// Asinh(x) calculates the inverse hyperbolic sine of x.
+//
+// Special cases are:
+//	Asinh(+Inf) = +Inf
+//	Asinh(-Inf) = -Inf
+//	Asinh(NaN) = NaN
+func Asinh(x float64) float64 {
+	const (
+		Ln2      = 6.93147180559945286227e-01 // 0x3FE62E42FEFA39EF
+		NearZero = 1.0 / (1 << 28)            // 2^-28
+		Large    = 1 << 28                    // 2^28
+	)
+	// TODO(rsc): Remove manual inlining of IsNaN, IsInf
+	// when compiler does it for us
+	// special cases
+	if x != x || x > MaxFloat64 || x < -MaxFloat64 { // IsNaN(x) || IsInf(x, 0)
+		return x
+	}
+	sign := false
+	if x < 0 {
+		x = -x
+		sign = true
+	}
+	var temp float64
+	switch {
+	case x > Large:
+		temp = Log(x) + Ln2 // |x| > 2^28
+	case x > 2:
+		temp = Log(2*x + 1/(Sqrt(x*x+1)+x)) // 2^28 > |x| > 2.0
+	case x < NearZero:
+		temp = x // |x| < 2^-28
+	default:
+		temp = Log1p(x + x*x/(1+Sqrt(1+x*x))) // 2.0 > |x| > 2^-28
+	}
+	if sign {
+		temp = -temp
+	}
+	return temp
+}