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# Differentiating complex numbers Watch

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?

Updated: April 15, 2012
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