Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2018/paper-1/6/a/solution

A space diagonal of the unit cube has displacement vector . Its Euclidean norm, or two successive applications of the Pythagorean theorem, gives
The requested diagonal joins opposite vertices; would be the diagonal of a face.

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