12 lines
No EOL
338 B
Text
12 lines
No EOL
338 B
Text
open nat
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example (n m : ℕ) : n + m = m + n :=
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begin
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induction m with m IHm,
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focus { induction n with n IHn,
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focus { reflexivity },
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focus { exact congr_arg succ IHn }},
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focus { apply eq.trans (congr_arg succ IHm),
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clear IHm, induction n with n IHn,
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focus { reflexivity },
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focus { exact congr_arg succ IHn }}
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end |