Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-oxford/2023/prelims/mathematics-i/4/b/ii/solution

Take the vector subspace of skew-symmetric matrices,
It is closed under vector addition and scalar multiplication, and a basis is
Indeed, its diagonal entries vanish, and its entries below the diagonal are forced by those above it. Hence . Part (a)(ii) proves that the only diagonalisable matrix in is .

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