blob: 2d4a044b87d2233b7c7eceb1d51f6d7ad41b2c96 (
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
|
// 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"
/*
* floating point tangent
*/
// Tan returns the tangent of x.
func Tan(x float64) float64 {
// Coefficients are #4285 from Hart & Cheney. (19.74D)
const
(
P0 = -.1306820264754825668269611177e+5;
P1 = .1055970901714953193602353981e+4;
P2 = -.1550685653483266376941705728e+2;
P3 = .3422554387241003435328470489e-1;
P4 = .3386638642677172096076369e-4;
Q0 = -.1663895238947119001851464661e+5;
Q1 = .4765751362916483698926655581e+4;
Q2 = -.1555033164031709966900124574e+3;
)
flag := false;
sign := false;
if(x < 0) {
x = -x;
sign = true;
}
x = x * (4/Pi); /* overflow? */
var e float64;
e, x = Modf(x);
i := int32(e);
switch i & 3 {
case 1:
x = 1 - x;
flag = true;
case 2:
sign = !sign;
flag = true;
case 3:
x = 1 - x;
sign = !sign;
}
xsq := x*x;
temp := ((((P4*xsq+P3)*xsq+P2)*xsq+P1)*xsq+P0)*x;
temp = temp/(((xsq+Q2)*xsq+Q1)*xsq+Q0);
if flag {
if(temp == 0) {
panic(NaN());
}
temp = 1/temp;
}
if sign {
temp = -temp;
}
return temp;
}
|
