# [SOLVED] complex dirvative first princple

• Feb 4th 2010, 12:01 PM
nerdo
[SOLVED] complex dirvative first princple

Attachment 15212

by using first princple
• Feb 4th 2010, 01:26 PM
shawsend
Just differentiate it like an ordinary function.
• Feb 4th 2010, 01:30 PM
nerdo
Quote:

Originally Posted by shawsend
Just differentiate it like an ordinary function.

I need to show it from first princple, which i am finding it hard 2 do.
• Feb 4th 2010, 04:08 PM
shawsend
You can do the $3z^2$ from the definition right? I'll do the other part:

Let $g(z)=i/z$

then:

$g'(z)=\lim_{\Delta z\to 0} \frac{\frac{i}{z+\Delta z}-\frac{i}{z}}{\Delta z}=\lim_{\Delta z\to 0}\frac{-i\Delta z}{z(z+\Delta z)\Delta z}=\lim_{\Delta z\to 0} \frac{-i}{z(z+\Delta z)}=-\frac{i}{z^2}$
• Feb 5th 2010, 06:20 AM
nerdo
THANKS FOR YOUR HELP. i MANAGE TO SOLVE THE PROBLEM AT THE END.