Fregier's Theorem

Fregier:=proc() local d,t,P,i,X,P2:

for i from 0 to 2 do   P[i]:=ParEllipse([0,0],d,t[i]):   od:

P[2]:=subs(t[2]=solve(   Slope(P[0],P[1])* Slope(P[0],P[2])=-1  , t[2]),P[2]):

X:=Pt (   NormalToEllipse ([0,0],d,t[0])  ,  Le(P[1],P[2])):

ItIsZero(normal(diff(X[1],t[1])))   and   ItIsZero(normal(diff(X[1],t[2]))):

end: