Theorem rappss ≪ | index | src | ≫ 

theorem rappss (A B: set) (a: nat): $ A C_ B -> A @' a C_ B @' a $;
StepHypRefExpression
1 ssel 
A C_ B -> a, a1 e. A -> a, a1 e. B
2 1 ssabd 
A C_ B -> {a1 | a, a1 e. A} C_ {a1 | a, a1 e. B}
3 2 conv rapp 
A C_ B -> A @' a C_ B @' a

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp, itru), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_10, ax_11, ax_12), axs_set (elab, ax_8)