2008-03-28 14:56:47 -06:00
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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2008-06-27 18:06:23 -06:00
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package math
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/*
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* Sinh(x) returns the hyperbolic sine of x
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*
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* The exponential func is called for arguments
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* greater in magnitude than 0.5.
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*
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* A series is used for arguments smaller in magnitude than 0.5.
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*
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* Cosh(x) is computed from the exponential func for
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* all arguments.
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*/
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// Sinh returns the hyperbolic sine of x.
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func Sinh(x float64) float64 {
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// The coefficients are #2029 from Hart & Cheney. (20.36D)
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const (
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P0 = -0.6307673640497716991184787251e+6;
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P1 = -0.8991272022039509355398013511e+5;
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P2 = -0.2894211355989563807284660366e+4;
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P3 = -0.2630563213397497062819489e+2;
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Q0 = -0.6307673640497716991212077277e+6;
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Q1 = 0.1521517378790019070696485176e+5;
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Q2 = -0.173678953558233699533450911e+3;
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)
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2009-03-05 14:31:01 -07:00
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sign := false;
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if x < 0 {
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x = -x;
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sign = true;
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}
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2008-11-19 17:14:31 -07:00
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var temp float64;
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switch true {
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case x > 21:
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temp = Exp(x)/2
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case x > 0.5:
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temp = (Exp(x)-Exp(-x))/2
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default:
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sq := x*x;
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temp = (((P3*sq + P2)*sq + P1)*sq + P0)*x;
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temp = temp/(((sq+Q2)*sq + Q1)*sq + Q0);
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}
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if sign {
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temp = -temp
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}
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return temp;
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}
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// Cosh returns the hyperbolic cosine of x.
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func Cosh(x float64) float64 {
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if x < 0 {
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x = -x
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}
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if x > 21 {
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return Exp(x)/2
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}
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return (Exp(x)+Exp(-x))/2;
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}
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