ref: becb89bae53e01785bfd843478737eeb77a9419f
dir: /sys/src/libc/port/sin.c/
/* C program for floating point sin/cos. Calls modf. There are no error exits. Coefficients are #3370 from Hart & Cheney (18.80D). */ #include <u.h> #include <libc.h> #define p0 .1357884097877375669092680e8 #define p1 -.4942908100902844161158627e7 #define p2 .4401030535375266501944918e6 #define p3 -.1384727249982452873054457e5 #define p4 .1459688406665768722226959e3 #define q0 .8644558652922534429915149e7 #define q1 .4081792252343299749395779e6 #define q2 .9463096101538208180571257e4 #define q3 .1326534908786136358911494e3 static double sinus(double arg, int quad) { double e, f, ysq, x, y, temp1, temp2; int k; x = arg; if(x < 0) { x = -x; quad += 2; } x *= 1/PIO2; /* underflow? */ if(x > 32764) { y = modf(x, &e); e += quad; modf(0.25*e, &f); quad = e - 4*f; } else { k = x; y = x - k; quad += k; quad &= 3; } if(quad & 1) y = 1-y; if(quad > 1) y = -y; ysq = y*y; temp1 = ((((p4*ysq+p3)*ysq+p2)*ysq+p1)*ysq+p0)*y; temp2 = ((((ysq+q3)*ysq+q2)*ysq+q1)*ysq+q0); return temp1/temp2; } double cos(double arg) { if(arg < 0) arg = -arg; return sinus(arg, 1); } double sin(double arg) { return sinus(arg, 0); }