Category : C Source Code
Archive   : CSRC2.ZIP
Filename : SIN.C

/* sin - sine and cosine functions */

/*
Based on the Yale CS "C" library. Coefficients are #3370 from
Hart and Cheney (18.80D)

Calls MODF
*/
extern double modf(); /* floating point modulus */
extern double itof(); /* integer to floating conversion */

static double twoopi = 0.63661977236758134308;
static double p0 = 0.1357884097877375669092680e8;
static double p1 = -.4942908100902844161158627e7;
static double p2 = 0.4401030535375266501944918e6;
static double p3 = -.1384727249982452873054457e5;
static double p4 = 0.1459688406665768722226959e3;
static double q0 = 0.8644558652922534429915149e7;
static double q1 = 0.4081792252343299749395779e6;
static double q2 = 0.9463096101538208180571257e4;
static double q3 = 0.1326534908786136358911494e3;

/* sinus - does the work for sine and cosine */

static double sinus(arg,quad)

double arg;
int quad;
{
double e,f;
double ysq,x,y;
int k;
double temp1,temp2;

x = arg;
if (x < 0)
{
x = -x;
quad += 2;
}
x = x*twoopi;
if (x > 32764.)
{
y = modf(x,&e);
e = e+ftoi(quad);
modf(0.25*e,&f);
quad = ftoi(e)-ftoi(4.0*f);
}
else
{
k = ftoi(x);
y = x-itof(k);
quad = (quad+k)&3;
}
if (quad&01) y = 1.0-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);
}

/* the sine and cosine calls */

double cos(arg)

double arg;
{
if (arg < 0.0) arg = -arg;
return(sinus(arg,1));
}

double sin(arg)

double arg;
{
return(sinus(arg,0));
}