Solution

ID: past-exam-of-the-short-options-paper-shared-by-parts-a-and-b-of-the-physics-course-of-the-university-of-oxford/2019/s1/3/d/solution

Use the branch cut and the branch of a multivalued function normalized by . The Laurent series from the preceding solution has coefficient . Consequently every sufficiently large positively oriented circle gives
Although grows cubically, its other Laurent series terms have zero contour integral. Choosing the opposite branch of a multivalued function reverses the sign; neither the branch of a multivalued function nor the orientation can be omitted from the answer.

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