Hint Resolve l8_2 : perp.
Ltac Perp := auto with perp.
Section T8_2.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.

Lemma l8_3 : forall A B C A',
Per A B C -> A<>B -> Col B A A' -> Per A' B C.