 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2026/ii/paper-1/4j/c/solution

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

f

is primitive recursive, then

d (n) = f (P_{1}^{1} (n), P_{1}^{1} (n))

is obtained by composition with projections. Hence the diagonal is primitive recursive.

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