You are Here: Home >< Maths

# Differentiating complex numbers

Announcements Posted on
Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. Hi
I'm having some difficulty with this simple question:
'Determine for what values of z (if any) the function f(z) = |z| is differentiable.'

My attempt:

Is this right? It seems too simple. Have I misunderstood the question?
2. modulus of z is root X^2 - Y^2 as i^2 = -1

Then I'm not sure, but I'm thinking you would differentiate implicitly by the chain rule if thats possible.
Is this FP2?
3. (Original post by Taurus)
modulus of z is root X^2 - Y^2 as i^2 = -1

Then I'm not sure, but I'm thinking you would differentiate implicitly by the chain rule if thats possible.
Is this FP2?
That's not right, the modulus of is . It's the distance from the origin (in the Argand diagram) of , which corresponds to the point .

By the looks of it this is first (maybe second) year undergraduate; differentiability definitely isn't in A-level!

(Original post by Muffin.)
Hi
I'm having some difficulty with this simple question:
'Determine for what values of z (if any) the function f(z) = |z| is differentiable.'

My attempt:

Is this right? It seems too simple. Have I misunderstood the question?
You just seem to have stated the answer without proving it. Plug it into the definition of differentiability and take some limits to justify your claim.
4. nooooo please dont say maths gets this hard!
5. [QUOTE=nuodai;37162583]That's not right, the modulus of is . It's the distance from the origin (in the Argand diagram) of , which corresponds to the point .

oh crap I knew that....
6. Have you done the Cauchy-Riemann differential equations?

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 15, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Who is getting a uni offer this half term?

Find out which unis are hot off the mark here

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams