Section T13.
Context `{TE:Tarski_euclidean}.

Lemma l12_23 :
forall A B C,
~Col A B C ->
exists B', exists C',
TS A C B B' /\ TS A B C C' /\
Bet B' A C' /\ CongA A B C B A C' /\ CongA A C B C A B'.