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[parent] Viewing Message
``Re: Nested prooves by contraction?'' by ratboy on 2008-07-02 02:50:54
> I'm just curious for an example of a valid proof by
> contradiction which contains (perhaps as the proof to one of
> its lemmas) another proof by contradiction.

The proof of the Feit-Thompson Theorem (http://planetmath.org/encyclopedia/FeitThompsonTheorem.html)is a proof by contradiction that includes countless lemmas proved by contradiction.

Browse the proof here (after gluing the two parts of the url together):
http://projecteuclid.org/DPubS?service=UI&version=1.0
&verb=Display&handle=euclid.pjm/1103053941
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