@options;

@figure;
  A = point( -4.3 , 8.03 )  { fixe };
  B = point( 9.57 , -7.9 )  { fixe };
  dAB = droite( A , B )  { rouge };
  C = point( -9.5 , 4.67 )  { fixe };
  D = point( 9.43 , -8.2 )  { fixe };
  dCD = droite( C , D );
  P = pointsur( dAB , 0.07 );
  Q = pointsur( dAB , 0.34 );
  R = pointsur( dCD , 0.14 );
  S = pointsur( dCD , 0.3 );
  sPR = segment( P , R )  { 3 };
  sPQ = segment( P , Q )  { 3 };
  sQS = segment( Q , S )  { 3 };
  sSR = segment( S , R )  { 3 };
  P' = pointsur( dAB , 0.49 );
  paraP'sPR = parallele( P' , sPR )  { 7 };
  paraP'dAB = parallele( P' , dAB );
  sPS = segment( P , S )  { orange , 7 };
  paraP'sPS = parallele( P' , sPS )  { 7 };
  S' = intersection( paraP'sPS , dCD );
  R' = intersection( paraP'sPR , dCD );
  paraS'sQS = parallele( S' , sQS )  { 7 };
  Q' = intersection( paraS'sQS , dAB );
  sP'Q' = segment( P' , Q' )  { rougefonce , 3 };
  sP'R' = segment( P' , R' )  { rougefonce , 3 };
  sR'S' = segment( R' , S' )  { rougefonce , 3 };
  sS'Q' = segment( S' , Q' )  { rougefonce , 3 };

@analyse;
P'Q' = 3.29
PQ = 5.7
calc(P'Q'/PQ) = 0.58