Description: Lemma for axdc3 . We have constructed a "candidate set" S , which consists of all finite sequences s that satisfy our property of interest, namely s ( x + 1 ) e. F ( s ( x ) ) on its domain, but with the added constraint that s ( 0 ) = C . These sets are possible "initial segments" of theinfinite sequence satisfying these constraints, but we can leverage the standard ax-dc (with no initial condition) to select a sequence of ever-lengthening finite sequences, namely ( hn ) : m --> A (for some integer m ). We let our "choice" function select a sequence whose domain is one more than the last one, and agrees with the previous one on its domain. Thus, the application of vanilla ax-dc yields a sequence of sequences whose domains increase without bound, and whose union is a function which has all the properties we want. In this lemma, we show that given the sequence h , we can construct the sequence g that we are after. (Contributed by Mario Carneiro, 30-Jan-2013)
Ref | Expression | ||
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Hypotheses | axdc3lem2.1 | |
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axdc3lem2.2 | |
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axdc3lem2.3 | |
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Assertion | axdc3lem2 | |