Description: Value of the first projection of a monuple. (Contributed by BJ, 6-Apr-2019)
Ref | Expression | ||
---|---|---|---|
Assertion | bj-pr11val |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-bj-1upl | ||
2 | bj-pr1eq | ||
3 | 1 2 | ax-mp | |
4 | bj-pr1val | ||
5 | eqid | ||
6 | 5 | iftruei | |
7 | 3 4 6 | 3eqtri |