\fo\or分配右侧(左侧不出现)
theorem fo_or_distrs_nfls {x: set} (A B: wff x):
$ \nf x A $ >
$ \fo x (A \or B) \iff A \or \fo x B $;
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | hyp n | \nf x A |
|
| 2 | 1 | _nf_clos_neg | \nf x \neg A |
| 3 | 2 | fo_imp_distrs_nfls | \fo x (\neg A \imp B) \iff \neg A \imp \fo x B |
| 4 | 3 | conv or | \fo x (A \or B) \iff A \or \fo x B |