# Math Help - Proof a complex function is harmonic

1. ## Proof a complex function is harmonic

hi guys!
i have problem proving this :
"f(z) is holomorphic on D (which does not contain 0).
prove that g(z)=ln|f(z)| is harmonic on D."
Note that D is a subset of C.
any ideas?

2. ## Re: Proof a complex function is harmonic

Hey Eleni.

What are the conditions for harmonic? Is it just using the Laplace definition?

3. ## Re: Proof a complex function is harmonic

Yea laplace and also when f(z)=u(x,y)+w(x,y)i is holomorphic then u, w are harmonic. Dont know if it helps but thats all i know

4. ## Re: Proof a complex function is harmonic

You will probably have to use the Cauchy Riemann equations to prove this.