10 lines
260 B
Text
10 lines
260 B
Text
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import data.nat
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open nat
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example : ∀ a b, a + b = b + a :=
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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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