Theorem albi ≪ | index | src | ≫ 

theorem albi (a: wff) {x: nat}: $ A. x a <-> a $;
StepHypRefExpression
1 eal 
A. x a -> a
2 ial 
a -> A. x a
3 1, 2 ibii 
A. x a <-> a

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_12)