Theorem eqrd ≪ | index | src | ≫ 

theorem eqrd (A B: set) (G: wff) {x: nat}:
  $ G -> (x e. A <-> x e. B) $ >
  $ G -> A == B $;
StepHypRefExpression
1 hyp h 
G -> (x e. A <-> x e. B)
2 1 iald 
G -> A. x (x e. A <-> x e. B)
3 2 conv eqs 
G -> A == B

Axiom use

axs_prop_calc (ax_1, ax_2, ax_mp), axs_pred_calc (ax_gen, ax_4, ax_5)