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Theorem xorbi12iOLD 1517
 Description: Obsolete version of xorbi12i 1516 as of 21-Apr-2024. (Contributed by Mario Carneiro, 4-Sep-2016.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypotheses
Ref Expression
xorbi12.1 (𝜑𝜓)
xorbi12.2 (𝜒𝜃)
Assertion
Ref Expression
xorbi12iOLD ((𝜑𝜒) ↔ (𝜓𝜃))

Proof of Theorem xorbi12iOLD
StepHypRef Expression
1 xorbi12.1 . . . 4 (𝜑𝜓)
2 xorbi12.2 . . . 4 (𝜒𝜃)
31, 2bibi12i 343 . . 3 ((𝜑𝜒) ↔ (𝜓𝜃))
43notbii 323 . 2 (¬ (𝜑𝜒) ↔ ¬ (𝜓𝜃))
5 df-xor 1503 . 2 ((𝜑𝜒) ↔ ¬ (𝜑𝜒))
6 df-xor 1503 . 2 ((𝜓𝜃) ↔ ¬ (𝜓𝜃))
74, 5, 63bitr4i 306 1 ((𝜑𝜒) ↔ (𝜓𝜃))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   ↔ wb 209   ⊻ wxo 1502 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-xor 1503 This theorem is referenced by: (None)
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