Section T8_4.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma perp_cong : forall A B P R X,
A <> B -> A <> P ->
Perp A B P A -> Perp A B R B ->
Cong A P B R -> Col A B X -> Bet P X R ->
Cong A R P B.