The GATE Grind

GATE 2016 EE (EE2) – Question 16

Engineering Mathematics · Complex Variables: Analytic functions, Cauchy integral formula, Taylor series, Laurent series, Residue theorem · 1 mark · Multiple choice

For complex z, let $f(z)=z+z^*$, where * denotes conjugation. Which is true?

  1. continuous and analytic
  2. continuous but not analytic
  3. not continuous but analytic
  4. neither continuous nor analytic

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) continuous but not analytic

Explanation

Write z=x+iy. Then f(z)=2x+j0, so u=2x and v=0 are continuous everywhere.

The Cauchy–Riemann condition ux=vy would require 2=0, which fails at every point. Thus f is nowhere complex differentiable, although continuous. The correct choice is **B**.

More Complex Variables: Analytic functions, Cauchy integral formula, Taylor series, Laurent series, Residue theorem questions

All Complex Variables: Analytic functions, Cauchy integral formula, Taylor series, Laurent series, Residue theorem questions →