Hi,
can anyone help me with this problem? I have included what working I can do, but I can't see any way of even getting close to the expected answer!
Much grovelling!

 

Try this for the nominator:
\(1-e^{j \omega T}=\\
1-\cos( \omega T)+j\cdot \sin( \omega T)\\
\\
abs(1-\cos( \omega T)+j\cdot \sin( \omega T))=\\
\sqrt{(1-\cos( \omega T))^2 + \sin^2( \omega T)}=\\
\sqrt{1-2cos( \omega T)+\cos^2( \omega T)+\sin^2( \omega T)}\)

Can you continue?
You will also need the equation \(\cos(x)=2\cos^2\left( \frac{x}{2} \right) -1\).

Solve this and we 'll see the angle next.

 

Also remember that \(|z|^2 = zz^*\) is a handy relation, especially for complex exponentials (* denotes the conjugate).

 

Thanks for the pointers- I solved it in the end! Hooray!