This is tan.c in view mode; [Download] [Up]
static double pid4= 0.7853981633974483096;
static double pid2= 1.5707963267948966192;
static double pi = 3.1415926535897932384;
double tan(x)
double x;
{
/*
Routine for the tangent. It puts x in the range 0-pi/4.
Then it uses a 6,6 Maehly approximation.
Derived and coded by J.A.M.Vermaseren 21-apr-1992.
*/
double fmod(),sum,x2;
int sflag, pflag;
if ( x < 0 ) { sflag = 1; x = -x; }
else sflag = 0;
if ( x >= pi ) x = fmod(x,pi);
if ( x >= pid2 ) { x = pi - x; sflag = 1 - sflag; }
if ( x > pid4 ) { pflag = 1; x = pid2 - x; }
else pflag = 0;
x2 = x*x;
sum = x*(-4797.60570220792587597407+x2*(
615.45028715821815261900+x2*(
-13.46133040142504243340+x2*
0.03590005535592163977)))/(
-4797.60570220792579574817+x2*(
2214.65218789418096945538+x2*(
-111.99796607144895992639+x2)));
if ( pflag ) sum = 1./sum;
if ( sflag ) return(-sum);
else return(sum);
}
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