assume(a1=0.3);
assume(a2=0.4);
O:=point(0);
J:=point(1);
T0:=droite(O,J);
[(D1:=droite(O,point(1+i*tan(a1)))),
 (D2:=droite(O,point(1+i*texpand(tan(2*a1))))),
 (D3:=droite(J,point(i*texpand(tan(2*a2))))),
 (D4:=droite(J,point(i*texpand(tan(a2))))),0];
T1:=droite(0,point(1+i*texpand(tan(3*a1))));
T2:=droite(J,point(i*texpand(tan(3*a2))));
A:=inter(T1,T2)[0];
[(D5:=droite(A,A+1+i*texpand(tan(pi/3+2*a1-a2)))),
 (D6:=droite(A,A+1+i*texpand(tan(2*pi/3+a1-2*a2)))),0];
B:=point(normal(affixe(inter(D1,D4)[0])));
C:=point(normal(affixe(inter(D3,D6)[0])));
D:=point(normal(affixe(inter(D5,D2)[0])));
triangle(B,C,D);
[segment(J,B),segment(J,C),segment(O,B),segment(O,D),segment(A,C),segment(A,D)];
bc:=longueur2(B,C);
dc:=longueur2(D,C);
db:=longueur2(D,B);
normal(bc-db);
normal(bc-dc);
xyztrange(-0.1,1.10, -0.10,1.10, -10.0,10.0, -1.0,6.0, -0.1,1.1, -0.1,1.1,0);