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 returns the inverse hyperbolic sine of x. Special cases are: Asinh(±0) = ±0 Asinh(±Inf) = ±Inf Asinh(NaN) = NaN
func ( float64) float64

func ( float64) float64 {
	const (
		      = 6.93147180559945286227e-01 // 0x3FE62E42FEFA39EF
		 = 1.0 / (1 << 28)            // 2**-28
		    = 1 << 28                    // 2**28
special cases
	if IsNaN() || IsInf(, 0) {
		return 
	}
	 := false
	if  < 0 {
		 = -
		 = true
	}
	var  float64
	switch {
	case  > :
		 = Log() +  // |x| > 2**28
	case  > 2:
		 = Log(2* + 1/(Sqrt(*+1)+)) // 2**28 > |x| > 2.0
	case  < :
		 =  // |x| < 2**-28
	default:
		 = Log1p( + */(1+Sqrt(1+*))) // 2.0 > |x| > 2**-28
	}
	if  {
		 = -
	}
	return