Theorem oreq2 ≪ | index | src | ≫

theorem oreq2 (a _b1 _b2: wff): $ (_b1 <-> _b2) -> (a \/ _b1 <-> a \/ _b2) $;

Step	Hyp	Ref	Expression
1		id	(_b1 <-> _b2) -> (_b1 <-> _b2)
2	1	oreq2d	(_b1 <-> _b2) -> (a \/ _b1 <-> a \/ _b2)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)