2014-01-02 19:23:55 +00:00
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2014-01-05 20:05:08 +00:00
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variables a b c d e : Nat.
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variable f : Nat -> Nat.
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axiom H1 : f a = a.
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2014-01-02 19:23:55 +00:00
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2014-01-05 20:05:08 +00:00
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theorem T : f (f (f a)) = a
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2014-01-02 19:23:55 +00:00
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:= calc f (f (f a)) = f (f a) : { H1 }
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... = f a : { H1 }
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... = a : { H1 }.
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