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SUPPLEMENTARY MATERIAL (USERS' MATHBOXES)
Mathbox for Richard Penner
Natural addition of Cantor normal forms
nnawordexg
Metamath Proof Explorer
Description: If an ordinal, B , is in a half-open interval between some A and
the next limit ordinal, B is the sum of the A and some natural
number. This weakens the antecedent of nnawordex . (Contributed by RP , 7-Jan-2025)
Ref
Expression
Assertion
nnawordexg
|- ( ( A e. On /\ A C_ B /\ B e. ( A +o _om ) ) -> E. x e. _om ( A +o x ) = B )
Proof
Step
Hyp
Ref
Expression
1
simp1
|- ( ( A e. On /\ A C_ B /\ B e. ( A +o _om ) ) -> A e. On )
2
omelon
|- _om e. On
3
2
a1i
|- ( ( A e. On /\ A C_ B /\ B e. ( A +o _om ) ) -> _om e. On )
4
3simpc
|- ( ( A e. On /\ A C_ B /\ B e. ( A +o _om ) ) -> ( A C_ B /\ B e. ( A +o _om ) ) )
5
oawordex2
|- ( ( ( A e. On /\ _om e. On ) /\ ( A C_ B /\ B e. ( A +o _om ) ) ) -> E. x e. _om ( A +o x ) = B )
6
1 3 4 5
syl21anc
|- ( ( A e. On /\ A C_ B /\ B e. ( A +o _om ) ) -> E. x e. _om ( A +o x ) = B )