blob: 78b3c299d668931fb0289328a99b0ab5ce29f723 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
// 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.
//
// Special cases are:
//
// Sinh(±0) = ±0
// Sinh(±Inf) = ±Inf
// Sinh(NaN) = NaN
func Sinh(x float64) float64 {
if haveArchSinh {
return archSinh(x)
}
return sinh(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 {
case x > 21:
temp = Exp(x) * 0.5
case x > 0.5:
ex := Exp(x)
temp = (ex - 1/ex) * 0.5
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.
//
// Special cases are:
//
// Cosh(±0) = 1
// Cosh(±Inf) = +Inf
// Cosh(NaN) = NaN
func Cosh(x float64) float64 {
if haveArchCosh {
return archCosh(x)
}
return cosh(x)
}
func cosh(x float64) float64 {
x = Abs(x)
if x > 21 {
return Exp(x) * 0.5
}
ex := Exp(x)
return (ex + 1/ex) * 0.5
}
|