2015-08-07 17:25:54 +00:00
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import data.nat
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2015-10-14 19:27:09 +00:00
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open nat algebra
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2015-08-07 17:25:54 +00:00
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2015-10-13 22:39:03 +00:00
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example : ∀ a b : nat, a + b = b + a :=
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2015-08-07 17:25:54 +00:00
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show ∀ a b : nat, a + b = b + a
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| 0 0 := rfl
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| 0 (succ b) := by rewrite zero_add
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| (succ a) 0 := by rewrite zero_add
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| (succ a) (succ b) := by rewrite [succ_add, this]
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