# Complex Variables : Analytic Functions and Limits

Please help with the following mathematics-related problem.

Let f(z) be analytic in a region G and setphi(z,w) = (f(w)-f(z))/(w-z) for w,z E G w does not equal z. Let z0 Ye G. Show that lim (z,w)-->(z0,z0) phi(z,w) =f'(z0).

Complex Variables. See attached file for full problem description

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#### Solution Preview

A proof needs to use some properties of ANALYTIC function.

You must have some definitions of an analytic function in your textbook(s) or lecture notes, but just in case here is a link to a web page with a definition:

http://en.wikipedia.org/wiki/Analytic_function

The proof that you have already received is probably based on either the infinite differentiability of an analytic function or on its expandability in Taylor series,

f(t) = f(z0) + f'(z0)(t-z0) +(1/2) ...

#### Solution Summary

The following posting helps with a mathematics-related problem. Analytic functions and limits are investigated in the answer. The solution is detailed and well presented. The response received a rating of "5/5" from the student who originally posted the question.