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Definition df-1st 5709
Description: Define a function that extracts the first member, or abscissa, of an ordered pair. Theorem op1st 5715 proves that it does this. For example, ( 1st `  <. 3 , 4  >.) = 3 . Equivalent to Definition 5.13 (i) of [Monk1] p. 52 (compare op1sta 4745 and op1stb 4175). The notation is the same as Monk's. (Contributed by NM, 9-Oct-2004.)
Assertion
Ref Expression
df-1st  1st  _V  |->  U.
dom  { }

Detailed syntax breakdown of Definition df-1st
StepHypRef Expression
1 c1st 5707 . 2  1st
2 vx . . 3  setvar
3 cvv 2551 . . 3  _V
42cv 1241 . . . . . 6
54csn 3367 . . . . 5  { }
65cdm 4288 . . . 4  dom  { }
76cuni 3571 . . 3  U. dom  { }
82, 3, 7cmpt 3809 . 2  _V  |->  U. dom  { }
91, 8wceq 1242 1  1st  _V  |->  U.
dom  { }
Colors of variables: wff set class
This definition is referenced by:  1stvalg  5711  fo1st  5726  f1stres  5728
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