Section PythagoreanFun.
Context `{T2D:Tarski_2D}.
Context `{TE:@Tarski_euclidean Tn TnEQD}.

Lemma opp_same_square : forall O E E' A B A2, Opp O E E' A B -> Prod O E E' A A A2 -> Prod O E E' B B A2.