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Definition df-id 4281
Description: Define the identity relation. Definition 9.15 of [Quine] p. 64. For example,  5  _I  5 and 
-.  4  _I  5 (ex-id 20765). (Contributed by NM, 13-Aug-1995.)
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 4276 . 2  class  _I
2 vx . . . 4  set  x
3 vy . . . 4  set  y
42, 3weq 1620 . . 3  wff  x  =  y
54, 2, 3copab 4050 . 2  class  { <. x ,  y >.  |  x  =  y }
61, 5wceq 1619 1  wff  _I  =  { <. x ,  y
>.  |  x  =  y }
Colors of variables: wff set class
This definition is referenced by:  dfid3  4282  ideqg  4823  cnvi  5073  dffun2  5204
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