2014-02-10 22:01:08 +00:00
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theorem symm_iff (p q : Bool) (H : p ↔ q) : (q ↔ p)
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:= symm H
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2014-02-17 20:05:34 +00:00
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theorem or_imp2 (p q : Bool) : (p ∨ q) ↔ (¬ p → q)
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2014-02-10 22:01:08 +00:00
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:= let H1 := symm_iff _ _ (imp_or (¬ p) q) in
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let H2 := not_not_eq p in
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let H3 := subst H1 H2 in
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H3
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