 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/iii/paper-303/3/c/solution

For generic

μ^{2} \neq = λ^{2}

, the symmetry is

O (1) \times O (2)

: an independent sign flip of

ϕ_{1}

(ϕ_{2}, ϕ_{3})

. When

μ^{2} = λ^{2}

, it is enhanced to

O (3)

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