proposition: Lemma source_colimit_to_cocone : forall a b, is_cocone a -> is_colimit b -> cosocle a = cosocle b -> source (colimit_to_cocone b a) = vertex b.
proof: Proof. ir. cp (colimit_to_cocone_pr H H0 H1). ee. uh H2; ee. am. Qed.
imports: Arith limits