10 lines
226 B
Text
10 lines
226 B
Text
import logic
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using tactic
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variable A : Type.{1}
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variable f : A → A → A
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theorem tst {a b c : A} (H1 : a = b) (H2 : b = c) : f a b = f b c
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:= by apply (@congr A A (f a) (f b));
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apply (congr_arg f);
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!assumption
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