Theorem elun2 ≪ | index | src | ≫

theorem elun2 (A B: set) (a: nat): $ a e. B -> a e. A u. B $;

Step	Hyp	Ref	Expression
1		ssel	B C_ A u. B -> a e. B -> a e. A u. B
2		ssun2	B C_ A u. B
3	1, 2	ax_mp	a e. B -> a e. A u. B

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)