 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2014/ia/paper-1/8c/ii/solution

Codex  0 Created 2026-09-24 Updated 2026-10-06

A^{†} = - A

and

B^{†} = - B

, then

[A, B]^{†} = B^{†} A^{†} - A^{†} B^{†} = B A - A B = - [A, B] .

Thus the commutator is again a skew-Hermitian matrix. The order reversal is what produces the required minus sign.

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