Description: Definition of the second projection of a class tuple. New usage is discouraged because the precise definition is generally unimportant compared to the characteristic properties bj-pr2eq , bj-pr22val , bj-pr2ex . (Contributed by BJ, 6-Oct-2018) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-bj-pr2 | |- pr2 A = ( 1o Proj A ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 0 | cA | |- A | |
| 1 | 0 | bj-cpr2 | |- pr2 A | 
| 2 | c1o | |- 1o | |
| 3 | 2 0 | bj-cproj | |- ( 1o Proj A ) | 
| 4 | 1 3 | wceq | |- pr2 A = ( 1o Proj A ) |