proposition: Lemma morphimIG A G : 'ker f \subset G -> f @* (A :&: G) = f @* A :&: f @* G.
proof: Proof. by move=> sKG; rewrite setIC morphimGI // setIC. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup)