Theorem or_updr ≪ | index | src | ≫

\or右更新

theorem or_updr (A B C: wff): $ A \or B \imp (B \imp C) \imp A \or C $;

Step	Hyp	Ref	Expression
1		imp_imp_swapl	((B \imp C) \imp A \or B \imp A \or C) \imp A \or B \imp (B \imp C) \imp A \or C
2		imp_introl_or	(B \imp C) \imp A \or B \imp A \or C
3	1, 2	ax_mp	A \or B \imp (B \imp C) \imp A \or C

Axiom use

Logic (ax_mp, ax_1, ax_2)