Description: Absorption of difference by union. This decomposes a union into two disjoint classes (see disjdif ). Theorem 35 of Suppes p. 29. (Contributed by NM, 19-May-1998)
Ref | Expression | ||
---|---|---|---|
Assertion | undif1 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | undir | |
|
2 | invdif | |
|
3 | 2 | uneq1i | |
4 | uncom | |
|
5 | unvdif | |
|
6 | 4 5 | eqtri | |
7 | 6 | ineq2i | |
8 | inv1 | |
|
9 | 7 8 | eqtri | |
10 | 1 3 9 | 3eqtr3i | |