proposition: Lemma orbit_trans G x y z : x \in orbit to G y -> y \in orbit to G z -> x \in orbit to G z.
proof: Proof. exact/orbit_in_trans/subsetT. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)