Lemma line_extension_reverse_bet : forall {Tm: Tarski_neutral_dimensionless} {Tm2: Tarski_neutral_dimensionless_with_decidable_point_equality Tm} (f : @Tpoint Tn -> @Tpoint Tm) P Q, line_extension f P Q -> forall A B C, Col P Q A -> Col P Q B -> Col P Q C -> Bet (f A) (f B) (f C) -> Bet A B C.