(** * Proposition 6 If in a triangle two angles be equal to one another, the sides which subtend the equal angles will also be equal to one another. *)
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(** * Proposition 8 If two triangles have the two sides equal to two sides respectively, and have also the base equal to the base, they will also have the angles equal which are contained by the equal straight lines. *)
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Lemma prop_8 : forall A B C D E F, A <> B -> A <> C -> B <> C ->
Cong A B D E -> Cong A C D F -> Cong B C E F ->
CongA B A C E D F /\ CongA A B C D E F /\ CongA B C A E F D.