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Theorem cases2ALT 1044
 Description: Alternate proof of cases2 1043, not using dedlema 1041 or dedlemb 1042. (Contributed by BJ, 6-Apr-2019.) (Proof shortened by Wolf Lammen, 2-Jan-2020.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
cases2ALT (((𝜑𝜓) ∨ (¬ 𝜑𝜒)) ↔ ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))

Proof of Theorem cases2ALT
StepHypRef Expression
1 pm3.4 809 . . . 4 ((𝜑𝜓) → (𝜑𝜓))
2 pm2.24 124 . . . . 5 (𝜑 → (¬ 𝜑𝜒))
32adantr 484 . . . 4 ((𝜑𝜓) → (¬ 𝜑𝜒))
41, 3jca 515 . . 3 ((𝜑𝜓) → ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))
5 pm2.21 123 . . . . 5 𝜑 → (𝜑𝜓))
65adantr 484 . . . 4 ((¬ 𝜑𝜒) → (𝜑𝜓))
7 pm3.4 809 . . . 4 ((¬ 𝜑𝜒) → (¬ 𝜑𝜒))
86, 7jca 515 . . 3 ((¬ 𝜑𝜒) → ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))
94, 8jaoi 854 . 2 (((𝜑𝜓) ∨ (¬ 𝜑𝜒)) → ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))
10 pm2.27 42 . . . . . 6 (𝜑 → ((𝜑𝜓) → 𝜓))
1110imdistani 572 . . . . 5 ((𝜑 ∧ (𝜑𝜓)) → (𝜑𝜓))
1211orcd 870 . . . 4 ((𝜑 ∧ (𝜑𝜓)) → ((𝜑𝜓) ∨ (¬ 𝜑𝜒)))
1312adantrr 716 . . 3 ((𝜑 ∧ ((𝜑𝜓) ∧ (¬ 𝜑𝜒))) → ((𝜑𝜓) ∨ (¬ 𝜑𝜒)))
14 pm2.27 42 . . . . . 6 𝜑 → ((¬ 𝜑𝜒) → 𝜒))
1514imdistani 572 . . . . 5 ((¬ 𝜑 ∧ (¬ 𝜑𝜒)) → (¬ 𝜑𝜒))
1615olcd 871 . . . 4 ((¬ 𝜑 ∧ (¬ 𝜑𝜒)) → ((𝜑𝜓) ∨ (¬ 𝜑𝜒)))
1716adantrl 715 . . 3 ((¬ 𝜑 ∧ ((𝜑𝜓) ∧ (¬ 𝜑𝜒))) → ((𝜑𝜓) ∨ (¬ 𝜑𝜒)))
1813, 17pm2.61ian 811 . 2 (((𝜑𝜓) ∧ (¬ 𝜑𝜒)) → ((𝜑𝜓) ∨ (¬ 𝜑𝜒)))
199, 18impbii 212 1 (((𝜑𝜓) ∨ (¬ 𝜑𝜒)) ↔ ((𝜑𝜓) ∧ (¬ 𝜑𝜒)))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 209   ∧ wa 399   ∨ wo 844 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845 This theorem is referenced by: (None)
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