Theorem nfsab ≪ | index | src | ≫

theorem nfsab {x y: nat} (A: set x y): $ FS/ y A $ > $ FS/ y S\ x, A $;

Step	Hyp	Ref	Expression
1		hyp h	FS/ y A
2	1	nfsbs	FS/ y S[fst a1 / x] A
3	2	nfel2	F/ y snd a1 e. S[fst a1 / x] A
4	3	nfab	FS/ y {a1 \| snd a1 e. S[fst a1 / x] A}
5	4	conv sab	FS/ y S\ x, 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)