Definition equilateral A B C :=
 Cong A B B C /\ Cong B C C A.Definition equilateral_strict A B C :=
 equilateral A B C /\ A <> B.

Lemma conga3_equilateral : forall A B C, ~ Col A B C -> CongA B A C A B C -> CongA A B C B C A -> equilateral A B C.