Description: Commutative law for equinumerosity of Cartesian product. Proposition 4.22(d) of Mendelson p. 254. (Contributed by NM, 27-Mar-2006)
Ref | Expression | ||
---|---|---|---|
Assertion | xpcomeng | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | xpeq1 | |
|
2 | xpeq2 | |
|
3 | 1 2 | breq12d | |
4 | xpeq2 | |
|
5 | xpeq1 | |
|
6 | 4 5 | breq12d | |
7 | vex | |
|
8 | vex | |
|
9 | 7 8 | xpcomen | |
10 | 3 6 9 | vtocl2g | |