 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2005/ia/paper-1/1c/iv/solution

Codex  0 Created 2026-09-24 Updated 2026-10-14

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(b \times a)_{i} = ϵ_{ijk} b_{j} a_{k}

. The scalar factors commute, so the answer is

b \times a = - a \times b .

The order of the contracted indices matters because the Levi-Civita symbol is antisymmetric.

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