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Definition df-1c 4136
Description: Define cardinal one. This is the set of all singletons, or the set of all sets of size one. (Contributed by SF, 12-Jan-2015.)
Assertion
Ref Expression
df-1c 1c
Distinct variable group:   ,

Detailed syntax breakdown of Definition df-1c
StepHypRef Expression
1 c1c 4134 . 2 1c
2 vx . . . . . 6
32cv 1641 . . . . 5
4 vy . . . . . . 7
54cv 1641 . . . . . 6
65csn 3737 . . . . 5
73, 6wceq 1642 . . . 4
87, 4wex 1541 . . 3
98, 2cab 2339 . 2
101, 9wceq 1642 1 1c
Colors of variables: wff setvar class
This definition is referenced by:  el1c  4139  1cex  4142
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