Solution

ID: past-exam-of-the-algebra-analysis-and-differential-equations-2-course-of-the-university-of-oxford/2009/analysis/6/b/solution

For a positively oriented simple closed piecewise smooth curve, a point inside it and a function holomorphic on a neighborhood of the curve and its interior, Cauchy's differentiated integral formula is
The printed denominator uses while the derivative and factorial use . The standard formula requires these indices to agree; the intended exponent in this display is . The private transcription preserves the mismatch exactly.
For the following task, write near zero with . Thus extends holomorphically at zero, and is holomorphic inside the specified contour because has no other zeros there. Now . Apply the correctly indexed formula with derivative order to get
Positive winding one supplies the orientation and multiplicity used in this expression.

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