Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2010/paper-2/14/b/i/solution

The transpose rule gives . If is orthogonal, , and the identity becomes
Multiplying on the left by yields . This is precisely the defining condition for an antisymmetric matrix.

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