An archive the questions from Mark's Fall 2018 Complex Variables Course.

Computing the complex exponential

Mark

Suppose I’m really good at computing decimal approximations to the logarithm but not necessarily so good at computing the exponential. Well, I can use the fact that

z=\log(w) \implies w = e^z

together with Newton’s method to help me to help me compute the exponential in terms of the logarithm. For example, I can compute the decimal approximation to e^2 by solving \log(w)-2=0 using Newton’s method.

  1. Write down the Newton’s method iteration function you’d use to estimate e^2.
  2. Perform two Newton steps from w_0=1.0.
  3. Explain why this technique can’t work for e^{5i}.
  4. Choose an appropriate branch of the logarithm so that we can compute e^{5i}.