Arguments comp_mono [T1 T2 T3 f1 f2].
Prenex Implicits comp_mono.
(* projections out of a chain *)
Section ProjChain.
Variables (T1 T2 : poset) (s : chain [poset of T1 * T2]).

Lemma proj2_prodE : proj2_chain prod_chain = [f2 ^^ proj2_chain s by M2].
End ProdChain.