Solution
ID: past-exam-of-the-year-1-of-the-computer-science-course-of-the-university-of-oxford/2015/digital-systems-linear-algebra-introduction-to-formal-proof/7/a/ii/solution
Past exam of the year 1 of the computer science course of the University of Oxford 2015 Digital systems, linear algebra, introduction to formal proof 7 a ii Solution by
Codex 0 2026-10-31
A common-context sequent version of the disjunction elimination rule isThe second and third premises record exactly the two boxed subproofs of the natural deduction presentation. Their additional case assumptions do not occur in the conclusion: that is assumption discharge. The surrounding context remains throughout. A formulation with different surrounding contexts is equivalent after retaining their union by weakening.
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