/* @(#)s_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. * ==================================================== */ /* sin(x) * Return sine function of x. * * kernel function: * __kernel_sin ... sine function on [-pi/4,pi/4] * __kernel_cos ... cose function on [-pi/4,pi/4] * __ieee754_rem_pio2 ... argument reduction routine * * Method. * Let S,C and T denote the sin, cos and tan respectively on * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 * in [-pi/4 , +pi/4], and let n = k mod 4. * We have * * n sin(x) cos(x) tan(x) * ---------------------------------------------------------- * 0 S C T * 1 C -S -1/T * 2 -S -C T * 3 -C S -1/T * ---------------------------------------------------------- * * Special cases: * Let trig be any of sin, cos, or tan. * trig(+-INF) is NaN, with signals; * trig(NaN) is that NaN; * * Accuracy: * TRIG(x) returns trig(x) nearly rounded */ #include "fdlibm.h" #ifdef __STDC__ double sin(double x) #else double sin(x) double x; #endif { double y[2],z=0.0; int n, ix; /* High word of x. */ ix = __HI(x); /* |x| ~< pi/4 */ ix &= 0x7fffffff; if(ix <= 0x3fe921fb) return __kernel_sin(x,z,0); /* sin(Inf or NaN) is NaN */ else if (ix>=0x7ff00000) return x-x; /* argument reduction needed */ else { n = __ieee754_rem_pio2(x,y); switch(n&3) { case 0: return __kernel_sin(y[0],y[1],1); case 1: return __kernel_cos(y[0],y[1]); case 2: return -__kernel_sin(y[0],y[1],1); default: return -__kernel_cos(y[0],y[1]); } } }