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Mirrors > Home > NFE Home > Th. List > df-nc | GIF version |
Description: Define the cardinality operation. This is the unique cardinal number containing a given set. Definition from [Rosser] p. 371. (Contributed by Scott Fenton, 24-Feb-2015.) |
Ref | Expression |
---|---|
df-nc | ⊢ Nc A = [A] ≈ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cA | . . 3 class A | |
2 | 1 | cnc 6091 | . 2 class Nc A |
3 | cen 6028 | . . 3 class ≈ | |
4 | 1, 3 | cec 5945 | . 2 class [A] ≈ |
5 | 2, 4 | wceq 1642 | 1 wff Nc A = [A] ≈ |
Colors of variables: wff setvar class |
This definition is referenced by: nceq 6108 ncex 6117 elncs 6119 ncidg 6122 ncprc 6124 elnc 6125 eqncg 6126 ncseqnc 6128 mucnc 6131 df0c2 6137 1cnc 6139 ncdisjeq 6148 |
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