 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2001/paper-1/10/a/iii/solution

The identity matrix has entries given by the Kronecker delta, so

tr I = δ_{ii} = n .

Each of the

n

diagonal entries is one.

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