Description: Deduction doubly substituting both sides of a biconditional. (Contributed by AV, 30-Jul-2023)
Ref | Expression | ||
---|---|---|---|
Hypotheses | sbbid.1 | |
|
sbbid.2 | |
||
2sbbid.1 | |
||
Assertion | 2sbbid | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sbbid.1 | |
|
2 | sbbid.2 | |
|
3 | 2sbbid.1 | |
|
4 | 3 2 | sbbid | |
5 | 1 4 | sbbid | |