ReactOS  0.4.15-dev-5649-gd5999c6
asin.c
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1 /*
2  * COPYRIGHT: See COPYING in the top level directory
3  * PROJECT: ReactOS CRT
4  * FILE: lib/sdk/crt/math/amd64/asin.c
5  * PURPOSE: Generic C implementation of arc sine
6  * PROGRAMMER: Timo Kreuzer (timo.kreuzer@reactos.org)
7  */
8 
9 #define PRECISION 9
10 
11 /*
12  * The arc sine can be approximated with the following row:
13  *
14  * asin(x) = a0*x + a1*x^3 + a2*x^5 + a3*x^7 + a4*x^9 + ...
15  *
16  * To reduce the number of multiplications the formula is transformed to
17  *
18  * asin(x) = x * (1 + x^2*(a1 + x^2*(a2 + x^2*(a3 + ...) ) ) )
19  *
20  * The coefficients are:
21  * a0 = 1
22  * a1 = (1/2*3)
23  * a2 = (3*1/4*2*5)
24  * a3 = (5*3*1/6*4*2*7)
25  * a4 = (7*5*3*1/8*6*4*2*9)
26  * a5 = (9*7*5*3*1/10*8*6*4*2*11)
27  * ...
28  */
29 
30 double
31 asin(double x)
32 {
33  double x2, result;
34 
35  /* Check range */
36  if ((x > 1.) || (x < -1.)) return NaN;
37 
38  /* Calculate the square of x */
39  x2 = (x * x);
40 
41  /* Start with 0, compiler will optimize this away */
42  result = 0;
43 
44  result += (15*13*11*9*7*5*3*1./(16*14*12*10*8*6*4*2*17));
45  result *= x2;
46 
47  result += (13*11*9*7*5*3*1./(14*12*10*8*6*4*2*15));
48  result *= x2;
49 
50  result += (11*9*7*5*3*1./(12*10*8*6*4*2*13));
51  result *= x2;
52 
53  result += (9*7*5*3*1./(10*8*6*4*2*11));
54  result *= x2;
55 
56  result += (7*5*3*1./(8*6*4*2*9));
57  result *= x2;
58 
59  result += (5*3*1./(6*4*2*7));
60  result *= x2;
61 
62  result += (3*1./(4*2*5));
63  result *= x2;
64 
65  result += (1./(2*3));
66  result *= x2;
67 
68  result += 1.;
69  result *= x;
70 
71  return result;
72 }
73 
GLuint64EXT * result
Definition: glext.h:11304
GLint GLint GLint GLint GLint x
Definition: gl.h:1548
double asin(double x)
Definition: asin.c:31
_In_ CLIPOBJ _In_ BRUSHOBJ _In_ LONG _In_ LONG _In_ LONG x2
Definition: winddi.h:3706