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Propositional calculus
imbi12d2a
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Theorem
imbi12d2a
Description:
Variant of
imbi12d2
.
(Contributed by
Zhi Wang
, 30-Aug-2024)
Ref
Expression
Hypotheses
imbi12d2.1
⊢
φ
→
ψ
↔
χ
imbi12d2a.2
⊢
φ
∧
ψ
→
θ
↔
τ
Assertion
imbi12d2a
⊢
φ
→
ψ
→
θ
↔
χ
→
τ
Proof
Step
Hyp
Ref
Expression
1
imbi12d2.1
⊢
φ
→
ψ
↔
χ
2
imbi12d2a.2
⊢
φ
∧
ψ
→
θ
↔
τ
3
2
ex
⊢
φ
→
ψ
→
θ
↔
τ
4
1
3
imbi12d2
⊢
φ
→
ψ
→
θ
↔
χ
→
τ