Step |
Hyp |
Ref |
Expression |
1 |
|
ifpidg |
⊢ ( ( 𝜓 ↔ if- ( 𝜑 , 𝜓 , 𝜒 ) ) ↔ ( ( ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ∧ ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ) ∧ ( ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ∧ ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ) ) ) |
2 |
|
simpr |
⊢ ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) |
3 |
2 2
|
pm3.2i |
⊢ ( ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ∧ ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ) |
4 |
3
|
biantrur |
⊢ ( ( ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ∧ ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ) ↔ ( ( ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ∧ ( ( 𝜑 ∧ 𝜓 ) → 𝜓 ) ) ∧ ( ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ∧ ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ) ) ) |
5 |
|
ancom |
⊢ ( ( ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ∧ ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ) ↔ ( ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ∧ ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ) ) |
6 |
1 4 5
|
3bitr2i |
⊢ ( ( 𝜓 ↔ if- ( 𝜑 , 𝜓 , 𝜒 ) ) ↔ ( ( 𝜓 → ( 𝜑 ∨ 𝜒 ) ) ∧ ( 𝜒 → ( 𝜑 ∨ 𝜓 ) ) ) ) |