Section EQUATIONS. (* Reference: "https://github.com/princeton-vl/CoqGym/blob/master/coq_projects/goedel/folLogic3.v" *)

Lemma proves_symmetry (Gamma : ensemble (frm L)) (t1 : trm L) (t2 : trm L)
(PROVE1 : Gamma \proves Eqn_frm t1 t2)
: Gamma \proves Eqn_frm t2 t1.