Section ActsSetop.
Variables (A : {set aT}) (S T : {set rT}).
Hypotheses (AactS : [acts A, on S | to]) (AactT : [acts A, on T | to]).

Lemma orbit_conjsg_in A a x y :
A \subset D -> a \in D ->
(to y a \in orbit to (A :^ a) (to x a)) = (y \in orbit to A x).