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Definition df-id 4767
Description: Define the identity relation. Definition 9.15 of [Quine] p. 64. (Contributed by SF, 5-Jan-2015.)
Assertion
Ref Expression
df-id I = {x, y x = y}
Distinct variable group:   x,y

Detailed syntax breakdown of Definition df-id
StepHypRef Expression
1 cid 4763 . 2 class I
2 vx . . . 4 setvar x
3 vy . . . 4 setvar y
42, 3weq 1643 . . 3 wff x = y
54, 2, 3copab 4622 . 2 class {x, y x = y}
61, 5wceq 1642 1 wff I = {x, y x = y}
Colors of variables: wff setvar class
This definition is referenced by:  dfid3  4768  ideqg  4868  ideqg2  4869  cnvi  5032
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