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Definition df-1st 4723
Description: Define a function that extracts the first member, or abscissa, of an ordered pair. (Contributed by SF, 5-Jan-2015.)
Assertion
Ref Expression
df-1st 1st = {x, y z x = y, z}
Distinct variable group:   x,y,z

Detailed syntax breakdown of Definition df-1st
StepHypRef Expression
1 c1st 4717 . 2 class 1st
2 vx . . . . . 6 setvar x
32cv 1641 . . . . 5 class x
4 vy . . . . . . 7 setvar y
54cv 1641 . . . . . 6 class y
6 vz . . . . . . 7 setvar z
76cv 1641 . . . . . 6 class z
85, 7cop 4561 . . . . 5 class y, z
93, 8wceq 1642 . . . 4 wff x = y, z
109, 6wex 1541 . . 3 wff z x = y, z
1110, 2, 4copab 4622 . 2 class {x, y z x = y, z}
121, 11wceq 1642 1 wff 1st = {x, y z x = y, z}
Colors of variables: wff setvar class
This definition is referenced by:  el1st  4729  df1st2  4738  br1st  4858
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