21 lines
539 B
Text
21 lines
539 B
Text
import logic
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theorem tst (a b : Prop) (H : a ↔ b) : b ↔ a
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:= have H1 [visible] : a → b, -- We need to mark H1 as fact, otherwise it is not visible by tactics
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from iff.elim_left H,
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by rapply iff.intro;
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intro Ha;
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apply (H1 Ha);
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intro Hb;
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apply (iff.elim_right H Hb)
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theorem tst2 (a b : Prop) (H : a ↔ b) : b ↔ a
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:= have H1 [visible] : a → b,
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from iff.elim_left H,
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begin
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rapply iff.intro,
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intro Ha;
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apply (H1 Ha),
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intro Hb;
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apply (iff.elim_right H Hb)
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end
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