Theorem cbvex ≪ | index | src | ≫

theorem cbvex {x y: nat} (p: wff x) (q: wff y):
  $ x = y -> (p <-> q) $ >
  $ E. x p <-> E. y q $;

Step	Hyp	Ref	Expression
1		nfv	F/ y p
2		nfv	F/ x q
3		hyp e	x = y -> (p <-> q)
4	1, 2, 3	cbvexh	E. x p <-> E. y q

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_10, ax_11, ax_12)