求sin()函数源代码
求一个C实现sin（）函数源代码





[解决办法]
C:\Android\Mydroid\bionic\libm\src\k_sin.c

C/C++ code

/* @(#)k_sin.c 1.3 95/01/18 *//* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */#ifndef lintstatic char rcsid[] = "$FreeBSD: src/lib/msun/src/k_sin.c,v 1.10 2005/11/02 13:06:49 bde Exp $";#endif/* __kernel_sin( x, y, iy) * kernel sin function on ~[-pi/4, pi/4] (except on -0), pi/4 ~ 0.7854 * Input x is assumed to be bounded by ~pi/4 in magnitude. * Input y is the tail of x. * Input iy indicates whether y is 0. (if iy=0, y assume to be 0). * * Algorithm *  1. Since sin(-x) = -sin(x), we need only to consider positive x. *  2. Callers must return sin(-0) = -0 without calling here since our *     odd polynomial is not evaluated in a way that preserves -0. *     Callers may do the optimization sin(x) ~ x for tiny x. *  3. sin(x) is approximated by a polynomial of degree 13 on *     [0,pi/4] *                   3            13 *      sin(x) ~ x + S1*x + ... + S6*x *     where * *  |sin(x)         2     4     6     8     10     12  |     -58 *  |----- - (1+S1*x +S2*x +S3*x +S4*x +S5*x  +S6*x   )| <= 2 *  |  x                               | * *  4. sin(x+y) = sin(x) + sin'(x')*y *          ~ sin(x) + (1-x*x/2)*y *     For better accuracy, let *           3      2      2      2      2 *      r = x *(S2+x *(S3+x *(S4+x *(S5+x *S6)))) *     then                   3    2 *      sin(x) = x + (S1*x + (x *(r-y/2)+y)) */#include "math.h"#include "math_private.h"static const doublehalf =  5.00000000000000000000e-01, /* 0x3FE00000, 0x00000000 */S1  = -1.66666666666666324348e-01, /* 0xBFC55555, 0x55555549 */S2  =  8.33333333332248946124e-03, /* 0x3F811111, 0x1110F8A6 */S3  = -1.98412698298579493134e-04, /* 0xBF2A01A0, 0x19C161D5 */S4  =  2.75573137070700676789e-06, /* 0x3EC71DE3, 0x57B1FE7D */S5  = -2.50507602534068634195e-08, /* 0xBE5AE5E6, 0x8A2B9CEB */S6  =  1.58969099521155010221e-10; /* 0x3DE5D93A, 0x5ACFD57C */double__kernel_sin(double x, double y, int iy){    double z,r,v;    z   =  x*x;    v   =  z*x;    r   =  S2+z*(S3+z*(S4+z*(S5+z*S6)));    if(iy==0) return x+v*(S1+z*r);    else      return x-((z*(half*y-v*r)-y)-v*S1);}