Theorem eqseq1 ≪ | index | src | ≫

theorem eqseq1 (_A1 _A2 B: set): $ _A1 == _A2 -> (_A1 == B <-> _A2 == B) $;

Step	Hyp	Ref	Expression
1		id	_A1 == _A2 -> _A1 == _A2
2	1	eqseq1d	_A1 == _A2 -> (_A1 == B <-> _A2 == 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_12), axs_set (ax_8)