#include "prototype.h"

/****** Function f_tangeant */

void f_tangeant(double *xg_tang_1, double *yg_tang_1, double xa, double ya, double ae, double r_gps);

 {

  
   double a_1_1, a_1_2, b_1_1, b_1_2, delta;
  

   delta=4*( (xa*xa)*(ya*ya) - ( ((xa*xa)-(ae*ae))*((ya*ya)-(ae*ae)) ));

   a_1_1= ( (2*xa*ya)+sqrt(delta) ) / ( 2*( (xa*xa)-(ae*ae) ) );
   a_1_2= ( (2*xa*ya)-sqrt(delta) ) / ( 2*( (xa*xa)-(ae*ae) ) );

   b_1_1=ae*sqrt(1+(a_1_1*a_1_1));
   b_1_2=ae*sqrt(1+(a_1_2*a_1_2));

   if (xa > 0)
     f_interbis(xg_tang_1, yg_tang_1, a_1_2, b_1_2, xa , ya, r_gps);
   else
     f_interbis(xg_tang_1, yg_tang_1, a_1_1, b_1_1, xa , ya, r_gps);

 }