Solution

ID: past-exam-of-the-algebra-analysis-and-differential-equations-2-course-of-the-university-of-oxford/2012/7/a/v/solution

A stable spiral has the complex conjugate eigenvalues
In suitable real coordinates the radius decays like while the angle changes at rate . The orbit therefore spirals towards the equilibrium, which is asymptotically stable. This is also called a stable focus.

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