@options;

@figure;
  R = point( -0.5 , -1 );
  cerayR3 = cerclerayon( R , 3 )  { i };
  T = pointsur( cerayR3 , 123.86 )  { (-0.83,-0.33) };
  sRT = segment( R , T );
  perpRsRT = perpendiculaire( R , sRT )  { i };
  cerayR4 = cerclerayon( R , 4 )  { i };
  S1 = intersection( perpRsRT , cerayR4 , 1 )  { i };
  S = intersection( perpRsRT , cerayR4 , 2 );
  sRS = segment( R , S );
  sTS = segment( T , S );
  angleSRT = angle( S , R , T );

@analyse;