Database
ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - add the Axiom of Infinity
Cardinal numbers
alephdom2
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alephle
Metamath Proof Explorer
Ascii
Unicode
Theorem
alephdom2
Description:
A dominated initial ordinal is included.
(Contributed by
Jeff Hankins
, 24-Oct-2009)
Ref
Expression
Assertion
alephdom2
⊢
A
∈
On
∧
B
∈
On
→
ℵ
⁡
A
⊆
B
↔
ℵ
⁡
A
≼
B
Proof
Step
Hyp
Ref
Expression
1
alephsdom
⊢
B
∈
On
∧
A
∈
On
→
B
∈
ℵ
⁡
A
↔
B
≺
ℵ
⁡
A
2
1
ancoms
⊢
A
∈
On
∧
B
∈
On
→
B
∈
ℵ
⁡
A
↔
B
≺
ℵ
⁡
A
3
2
notbid
⊢
A
∈
On
∧
B
∈
On
→
¬
B
∈
ℵ
⁡
A
↔
¬
B
≺
ℵ
⁡
A
4
alephon
⊢
ℵ
⁡
A
∈
On
5
4
onordi
⊢
Ord
⁡
ℵ
⁡
A
6
eloni
⊢
B
∈
On
→
Ord
⁡
B
7
ordtri1
⊢
Ord
⁡
ℵ
⁡
A
∧
Ord
⁡
B
→
ℵ
⁡
A
⊆
B
↔
¬
B
∈
ℵ
⁡
A
8
5
6
7
sylancr
⊢
B
∈
On
→
ℵ
⁡
A
⊆
B
↔
¬
B
∈
ℵ
⁡
A
9
8
adantl
⊢
A
∈
On
∧
B
∈
On
→
ℵ
⁡
A
⊆
B
↔
¬
B
∈
ℵ
⁡
A
10
domtriord
⊢
ℵ
⁡
A
∈
On
∧
B
∈
On
→
ℵ
⁡
A
≼
B
↔
¬
B
≺
ℵ
⁡
A
11
4
10
mpan
⊢
B
∈
On
→
ℵ
⁡
A
≼
B
↔
¬
B
≺
ℵ
⁡
A
12
11
adantl
⊢
A
∈
On
∧
B
∈
On
→
ℵ
⁡
A
≼
B
↔
¬
B
≺
ℵ
⁡
A
13
3
9
12
3bitr4d
⊢
A
∈
On
∧
B
∈
On
→
ℵ
⁡
A
⊆
B
↔
ℵ
⁡
A
≼
B