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// 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"
/*
* Sinh(x) returns the hyperbolic sine of x
*
* The exponential func is called for arguments
* greater in magnitude than 0.5.
*
* A series is used for arguments smaller in magnitude than 0.5.
*
* Cosh(x) is computed from the exponential func for
* all arguments.
*/
// Sinh returns the hyperbolic sine of x.
func Sinh(x float64) float64 {
// The coefficients are #2029 from Hart & Cheney. (20.36D)
const
(
P0 = -0.6307673640497716991184787251e+6;
P1 = -0.8991272022039509355398013511e+5;
P2 = -0.2894211355989563807284660366e+4;
P3 = -0.2630563213397497062819489e+2;
Q0 = -0.6307673640497716991212077277e+6;
Q1 = 0.1521517378790019070696485176e+5;
Q2 = -0.173678953558233699533450911e+3;
)
sign := false;
if x < 0 {
x = -x;
sign = true;
}
var temp float64;
switch true {
case x > 21:
temp = Exp(x)/2;
case x > 0.5:
temp = (Exp(x) - Exp(-x))/2;
default:
sq := x*x;
temp = (((P3*sq+P2)*sq+P1)*sq+P0)*x;
temp = temp/(((sq+Q2)*sq+Q1)*sq+Q0);
}
if sign {
temp = -temp;
}
return temp;
}
// Cosh returns the hyperbolic cosine of x.
func Cosh(x float64) float64 {
if x < 0 {
x = - x;
}
if x > 21 {
return Exp(x)/2;
}
return (Exp(x) + Exp(-x))/2;
}
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