Description: Disjunction inside and outside of a substitution are equivalent. (Contributed by NM, 29-Sep-2002)
Ref | Expression | ||
---|---|---|---|
Assertion | sbor | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sbim | |
|
2 | sbn | |
|
3 | 2 | imbi1i | |
4 | 1 3 | bitri | |
5 | df-or | |
|
6 | 5 | sbbii | |
7 | df-or | |
|
8 | 4 6 7 | 3bitr4i | |