Section T8_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma Perp_perm :
forall A B C D,
Perp A B C D ->
Perp A B C D /\ Perp B A C D /\ Perp A B D C /\ Perp B A D C /\
Perp C D A B /\ Perp C D B A /\ Perp D C A B /\ Perp D C B A.