8 lines
235 B
Text
8 lines
235 B
Text
theorem symm_iff (p q : Bool) (H : p ↔ q) : (q ↔ p)
|
||
:= symm H
|
||
|
||
theorem or_imp2 (p q : Bool) : (p ∨ q) ↔ (¬ p → q)
|
||
:= let H1 := symm_iff _ _ (imp_or (¬ p) q) in
|
||
let H2 := not_not_eq p in
|
||
let H3 := subst H1 H2 in
|
||
H3
|