www.pudn.com > 文件恢复及修补 C 语言源程序.zip > SINE.C

 
/*********************************************************** 
 *               The TULSA IBM C BOARD                     * 
 *                   918-664-8737                          * 
 *             300/1200 XMODEM, 24 Hours                   * 
 **********************************************************/ 
 
 
#include "math.h" 
#include "errno.h" 
 
double cos(x) 
double x; 
{ 
        double sincos(); 
 
        return sincos(x, fabs(x) + 1.57079632679489661923, 0); 
} 
 
double sin(x) 
double x; 
{ 
        double sincos(); 
 
        if (x < 0.0) 
                return sincos(x,-x,1); 
        else 
                return sincos(x,x,0); 
} 
 
#define R1 -0.16666666666666665052e+00 
#define R2 +0.83333333333331650314e-02 
#define R3 -0.19841269841201840457e-03 
#define R4 +0.27557319210152756119e-05 
#define R5 -0.25052106798274584544e-07 
#define R6 +0.16058936490371589114e-09 
#define R7 -0.76429178068910467734e-12 
#define R8 +0.27204790957888846175e-14 
 
#define YMAX 6.7465e09 
 
static double sincos(x,y,sgn) 
double x,y; 
{ 
        double f, xn, r, g; 
        extern int errno; 
 
        if (y >= YMAX) { 
                errno = ERANGE; 
                return 0.0; 
        } 
        if (modf(y * 0.31830988618379067154, &xn) >= 0.5) 
                ++xn; 
        if ((int)xn & 1) 
                sgn = !sgn; 
        if (fabs(x) != y) 
                xn -= 0.5; 
        g = modf(fabs(x), &x);          /* break into fraction and integer parts */ 
        f = ((x - xn*3.1416015625) + g) + xn*8.9089102067615373566e-6; 
        if (fabs(f) > 2.3283e-10) { 
                g = f*f; 
                r = (((((((R8*g R7)*g R6)*g R5)*g 
                                R4)*g R3)*g R2)*g R1)*g; 
                f += f*r; 
        } 
        if (sgn) 
                f = -f; 
        return f; 
}