Deriving the Group Delay of an LTI Discrete-Time System

[ElfenKiller]

Homework Statement

Show that the group delay of an LTI discrete-time system characterized by a frequency response $H(e^{j\omega})$ can be expressed as

$\tau(\omega)= Re\left\{\frac{j\frac{dH(e^{j\omega}}{d\omega}}{H(e^{j\omega}}\right\}$.

Homework Equations

The Attempt at a Solution

I think I understand the rest of the proof (not shown here) but I don't see why the equation in (2) is valid. First, I had the idea that the first term in the equation in (2) is the real part and the second term in the equation is the imaginary part of the derivative, but it does not really appear to me to be like that.

 

[ElfenKiller]

Found the solution by asking some friend. If someone wants to know it, let me know.