# Great Poncelet Theorem
Let(A=[x1,0], B=[x2,0], D=[0,x3], A1=[x4,x5], B1=[x6,x7], C=[x8,x9], 
    H=[x10,x11]):
Poncelet:=Theorem([arbitrary(A,B,D), reflection(A,D,B,B1),
                   reflection(B,D,A,A1), intersection(A,B1,B,A1,C),
                   circumcenter(A,B,C,H), r^2-x3^2,R^2-sdistance(H,A)],
                  R^2-2*R*r-sdistance(D,H), [x4,x5,x6,x7,x8,x9,x10,x11,r,R]);
