68 lines
1.3 KiB
Go
68 lines
1.3 KiB
Go
// 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
|
|
|
|
/*
|
|
Floating-point hyperbolic sine and cosine.
|
|
|
|
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
|
|
}
|