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Part BCSIR NET December 2024agreement-on-a-line-propagates-by-reflection

Agreement on a line propagates by reflection

For z = x + iy , let f(z) = u(x, y) + iv(x, y) define an entire function. Consider the function g(z) = u(x, −y) − iv(x, −y), for z = x + iy . Suppose that v(x, 0) = 0 for all . Define E = { | f(z) = g(z)}. Which of the following statements is true?

  1. A.E is the real axis.
  2. B.E is the imaginary axis.
  3. C.E contains an open subset of , but .
  4. D.

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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50 are analysed free — try those first.

Related counterexample: A harmonic function on any domain has a harmonic conjugate

More on this topic

The chapter behind this: Cauchy–Riemann — what they do and do not give you — free to read

From Analytic FunctionsCauchy–Riemann equations, harmonic functions

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