Database
ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - add the Axiom of Infinity
Eight inequivalent definitions of finite set
isfin32i
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isf33lem
Metamath Proof Explorer
Ascii
Unicode
Theorem
isfin32i
Description:
One half of
isfin3-2
.
(Contributed by
Mario Carneiro
, 3-Jun-2015)
Ref
Expression
Assertion
isfin32i
⊢
A
∈
Fin
III
→
¬
ω
≼
*
A
Proof
Step
Hyp
Ref
Expression
1
isfin3
⊢
A
∈
Fin
III
↔
𝒫
A
∈
Fin
IV
2
isfin4-2
⊢
𝒫
A
∈
Fin
IV
→
𝒫
A
∈
Fin
IV
↔
¬
ω
≼
𝒫
A
3
2
ibi
⊢
𝒫
A
∈
Fin
IV
→
¬
ω
≼
𝒫
A
4
relwdom
⊢
Rel
⁡
≼
*
5
4
brrelex1i
⊢
ω
≼
*
A
→
ω
∈
V
6
canth2g
⊢
ω
∈
V
→
ω
≺
𝒫
ω
7
sdomdom
⊢
ω
≺
𝒫
ω
→
ω
≼
𝒫
ω
8
5
6
7
3syl
⊢
ω
≼
*
A
→
ω
≼
𝒫
ω
9
wdompwdom
⊢
ω
≼
*
A
→
𝒫
ω
≼
𝒫
A
10
domtr
⊢
ω
≼
𝒫
ω
∧
𝒫
ω
≼
𝒫
A
→
ω
≼
𝒫
A
11
8
9
10
syl2anc
⊢
ω
≼
*
A
→
ω
≼
𝒫
A
12
3
11
nsyl
⊢
𝒫
A
∈
Fin
IV
→
¬
ω
≼
*
A
13
1
12
sylbi
⊢
A
∈
Fin
III
→
¬
ω
≼
*
A