input courbescp;
beginfig(1);
  depart((0,0),(10,10),(4,4),1,1);
  grille(1);
  axes;
  graduationx(btex $I$ etex);
  graduationy(btex $J$ etex);
  legendex(btex axe des abscisses etex);
  legendey(btex axe des ordonn\'ees etex);
  pair O,I,J,M,A,B;
  O=placepoint(0,0);
  I=placepoint(1,0);
  J=placepoint(0,1);
  A=placepoint(3,5);
  B=placepoint(1,-3);
  M=placepoint(-sqrt3,2*sqrt2);
  draw Projection(M);
  label.bot(btex $x_M$ etex,placepoint(-sqrt3,0));
  label.rt(btex $y_M$ etex,placepoint(0,2*sqrt2));
  label.ulft(btex $M$ etex,M);
  marquepoint(A);
  marquepoint(B);  
  label.urt(btex $A$ etex,A);
  label.llft(btex $B$ etex,B);
endfig;
beginfig(2);
 depart((0,0),(12,6),(6,3),1,1);
  grille(1);
  axes;
  graduationx(btex $I$ etex);
  graduationy(btex $J$ etex);
  pair A,B,C,D,E,F;
  A=placepoint(0,2);
  B=placepoint(-3,-2);
  C=placepoint(-5,0);
  D=placepoint(4,-1);
  E=placepoint(3,2);
  F=placepoint(5,1);
  drawarrow A--B;
  drawarrow D--C;
  drawarrow E--F;
  label.ulft(btex $A$ etex,A);
  label.bot(btex $B$ etex,B);
  label.ulft(btex $C$ etex,C);
  label.lrt(btex $D$ etex,D);
  label.ulft(btex $E$ etex,E);
  label.lrt(btex $F$ etex,F);
endfig;
beginfig(3);
 depart((0,0),(10,7),(6,2),1,1);
  grille(1);
  axes;
  graduationx(btex $I$ etex);
  graduationy(btex $J$ etex);
  pair A,B,C,D;
  A=placepoint(1,2);
  B=placepoint(-3,-1);
  C=placepoint(-5,4);
  D=placepoint(3,-1);
  draw A--B;
  draw D--C;
  marquepoint(A);
  marquepoint(B);
  marquepoint(C);
  marquepoint(D);  
  label.ulft(btex $A$ etex,A);
  label.bot(btex $B$ etex,B);
  label.ulft(btex $C$ etex,C);
  label.lrt(btex $D$ etex,D);
endfig;
beginfig(4);
 depart((0,0),(10,6.5),(6,2),0.5,0.5);
  grille(0.5);
  axes;
  graduationx(btex $I$ etex);
  graduationy(btex $J$ etex);
  pair A,B,C,D,K;
  A=placepoint(4,5);
  B=placepoint(0,-3);
  C=placepoint(-6,0);
  draw A--B--C--cycle;
  C-D=B-A;
  K=1/2[A,C];
  marquepoint(A);
  marquepoint(B);
  marquepoint(C);
  marquepoint(D);  
  marquepoint(K);
  label.ulft(btex $A$ etex,A);
  label.llft(btex $B$ etex,B);
  label.top(btex $C$ etex,C);
  label.urt(btex $D$ etex,D);
endfig;
end