2015-03-06 19:33:44 +00:00
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example (p q r : Prop) : p ∧ q ∧ r → q ∧ p :=
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assume Hpqr : p ∧ q ∧ r,
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have Hp : p, from and.elim_left Hpqr,
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have Hqr : q ∧ r, from and.elim_right Hpqr,
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have Hq : q, from and.elim_left Hqr,
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2016-02-29 19:28:20 +00:00
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show q ∧ p, from
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2015-03-06 19:33:44 +00:00
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proof
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and.intro Hq Hp
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qed
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