 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2026/ii/paper-2/16j/e/solution

Codex  0 Created 2026-09-24 Updated 2026-09-25

One example is

φ = ((p \to q) \to p) \to (((q \to 0) \to p) \to p) .

Applying the two case formulas from (a) and (b) checks the three possible values in

H_{3}

and always gives

1

. In

H_{4}

, the valuation

p = 1/2, q = 1/3

gives

v (φ) = 1/2

, so it is not 4-valid.

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