Description: Commutative law for class equality. Theorem 6.5 of Quine p. 41. (Contributed by NM, 26-May-1993) (Proof shortened by Wolf Lammen, 19-Nov-2019)
Ref | Expression | ||
---|---|---|---|
Assertion | eqcom | |
Step | Hyp | Ref | Expression |
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1 | id | |
|
2 | 1 | eqcomd | |
3 | id | |
|
4 | 3 | eqcomd | |
5 | 2 4 | impbii | |