[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?

[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?

[nuodai]

(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.

[pbsjohnz]

nooooo please dont say maths gets this hard!

[Taurus]

[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....

[Bobifier]

Have you done the Cauchy-Riemann differential equations?