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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2008-06-27 18:06:23 -06:00
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import math "exp"
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export sinh, cosh
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/*
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* sinh(arg) returns the hyperbolic sine of its floating-
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* point argument.
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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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* The coefficients are #2029 from Hart & Cheney. (20.36D)
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*
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* cosh(arg) is computed from the exponential func for
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* all arguments.
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*/
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const
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(
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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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func
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sinh(arg float64) float64
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{
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var temp, argsq float64;
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var sign bool;
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sign = false;
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if arg < 0 {
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arg = -arg;
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sign = true;
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}
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switch true {
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case arg > 21:
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temp = exp(arg)/2;
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case arg > 0.5:
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temp = (exp(arg) - exp(-arg))/2;
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default:
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argsq = arg*arg;
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temp = (((p3*argsq+p2)*argsq+p1)*argsq+p0)*arg;
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temp = temp/(((argsq+q2)*argsq+q1)*argsq+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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func
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cosh(arg float64) float64
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{
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if arg < 0 {
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arg = - arg;
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}
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if arg > 21 {
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return exp(arg)/2;
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}
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return (exp(arg) + exp(-arg))/2;
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}
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