Theorem rexal | index | src |

theorem rexal {x y: nat} (a: wff x) (b: wff x y):
  $ E. x (a /\ A. y b) -> A. y E. x (a /\ b) $;
StepHypRefExpression
1 alan1
A. y (a /\ b) <-> a /\ A. y b
2 1 exeqi
E. x A. y (a /\ b) <-> E. x (a /\ A. y b)
3 exal
E. x A. y (a /\ b) -> A. y E. x (a /\ b)
4 2, 3 sylbir
E. x (a /\ A. y b) -> A. y E. x (a /\ b)

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)