proposition: Lemma sdprodmE a b : a \in H -> b \in K -> sdprodm (a * b) = fH a * fK b.
proof: Proof. exact: pprodmE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)