Definition pairg1 x : gT1 * gT2 := (x, 1).
Definition pair1g x : gT1 * gT2 := (1, x).

Lemma morphim_sndX (H1: {group gT1}) (H2 : {set gT2}) :
[morphism of fun x => x.2] @* setX H1 H2 = H2.