/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

int main()
{
  picture(P(-1,0), P(1,1), "2.5 x 1.25in");

  begin();

  degrees();
  double th(120), d_th(10);
  P ptO(0,0), ptA(-1,0), ptB(1,0), ptC(0.4,0), ptP(cis(th)), ptP2(cis(th + d_th));

  //  double phi(Acos(((ptP - ptB)|E_1)/norm(ptP - ptB)));
  //  double phi2(Acos(((ptP2 - ptC)|E_1)/norm(ptP2 - ptC)));

  line(ptA, ptB);
  arc(ptO, 1, 0, 180);

  line(ptO, ptP);
  line(ptO, ptP2);

  line(ptC, ptP);
  line(ptC, ptP2);
  line(ptB, ptP);

  line(ptC, ptP);

  arc_measure(ptB, ptP - ptB, -E_1, P(-4,2), "$\\phi$", l, 16);
  arc_measure(ptC, ptP - ptC, -E_1, P(-2,2), "$\\phi_1$", l, 16);

  label(ptA, P(0,-4), "$A$", b);
  label(ptO, P(0,-4), "$O$", b);
  label(ptC, P(0,-4), "$C$", b);
  label(ptB, P(0,-4), "$B$", b);

  label(ptP, P(0,2), "$P$", tl);
  label(ptP2, P(-2,0), "$P'$", tl);

  tikz_format();
  end();
}