Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2015/ii/paper-3/7d/a/solution

The Hamiltonian is . On a regular family of closed phase-space trajectories, action-angle variables are canonical coordinates in which is periodic modulo and . Hamilton's equations then give and .
The action variable is
The orientation is that of the motion, so the integral is the positive enclosed phase-space area divided by .

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