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Part BCSIR NET December 2024a-double-pole-extracts-the-derivative

A double pole extracts the derivative

Let be the circle { : |z| = 3} oriented counterclockwise. Let f be an entire function. What is the value of A for which dz = 0 holds?

  1. A.f(1)
  2. B.f(2)
  3. C.f′(1)
  4. D.f′(2)

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward.

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Related counterexample: Cauchy's theorem applies to any domain without singularities of f

More on this topic

The chapter behind this: Cauchy's theorem and integral formula — the toolkit — free to read

From Cauchy TheoryCauchy's theorem and integral formula

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