2014-08-24 19:58:48 -07:00
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import logic
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2014-06-30 00:51:11 -07:00
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2014-07-22 09:43:18 -07:00
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theorem tst (a b : Prop) (H : a ↔ b) : b ↔ a
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2015-04-27 15:06:16 -07:00
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:= by apply iff.intro;
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2014-10-23 22:36:32 -07:00
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intro Hb;
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2015-04-27 15:06:16 -07:00
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apply (iff.elim_right H Hb);
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intro Ha;
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apply (iff.elim_left H Ha)
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2014-07-02 13:14:50 -07:00
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check tst
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