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Simtel MSDOS - Coast to Coast
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ANOMALY.C
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C/C++ Source or Header
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1990-09-13
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586b
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30 lines
#include <stdio.h>
#include <math.h>
#include "astro.h"
#define TWOPI (2*PI)
/* given the mean anomaly, ma, and the eccentricity, s, of elliptical motion,
* find the true anomaly, *nu, and the eccentric anomaly, *ea.
* all angles in radians.
*/
anomaly (ma, s, nu, ea)
double ma, s;
double *nu, *ea;
{
double m, dla, fea;
m = ma-TWOPI*(long)(ma/TWOPI);
fea = m;
while (1) {
dla = fea-(s*sin(fea))-m;
if (fabs(dla)<1e-6)
break;
dla /= 1-(s*cos(fea));
fea -= dla;
}
*nu = 2*atan(sqrt((1+s)/(1-s))*tan(fea/2));
*ea = fea;
}