s_sin.c (1935B)
1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 /* sin(x) 13 * Return sine function of x. 14 * 15 * kernel function: 16 * __kernel_sin ... sine function on [-pi/4,pi/4] 17 * __kernel_cos ... cose function on [-pi/4,pi/4] 18 * __ieee754_rem_pio2 ... argument reduction routine 19 * 20 * Method. 21 * Let S,C and T denote the sin, cos and tan respectively on 22 * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 23 * in [-pi/4 , +pi/4], and let n = k mod 4. 24 * We have 25 * 26 * n sin(x) cos(x) tan(x) 27 * ---------------------------------------------------------- 28 * 0 S C T 29 * 1 C -S -1/T 30 * 2 -S -C T 31 * 3 -C S -1/T 32 * ---------------------------------------------------------- 33 * 34 * Special cases: 35 * Let trig be any of sin, cos, or tan. 36 * trig(+-INF) is NaN, with signals; 37 * trig(NaN) is that NaN; 38 * 39 * Accuracy: 40 * TRIG(x) returns trig(x) nearly rounded 41 */ 42 43 #include "math_libm.h" 44 #include "math_private.h" 45 46 double sin(double x) 47 { 48 double y[2],z=0.0; 49 int32_t n, ix; 50 51 /* High word of x. */ 52 GET_HIGH_WORD(ix,x); 53 54 /* |x| ~< pi/4 */ 55 ix &= 0x7fffffff; 56 if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0); 57 58 /* sin(Inf or NaN) is NaN */ 59 else if (ix>=0x7ff00000) return x-x; 60 61 /* argument reduction needed */ 62 else { 63 n = __ieee754_rem_pio2(x,y); 64 switch(n&3) { 65 case 0: return __kernel_sin(y[0],y[1],1); 66 case 1: return __kernel_cos(y[0],y[1]); 67 case 2: return -__kernel_sin(y[0],y[1],1); 68 default: 69 return -__kernel_cos(y[0],y[1]); 70 } 71 } 72 } 73 libm_hidden_def(sin)