How to plot cosine of complex function of third degree?

I plot the phase of this function

fb(z) = (0.1496 − 0.1692i)z^−1 + (0.2472 + 0.0916i)z^−2 + (−0.8196 − 0.3718i)z^−3

by using this command

surf(re_z,im_z,angle(f_of_z_result),'EdgeColor','none'); .

My question is how can me plot the cosine of this function?

I appriciate any help

[Chunru]

do you mean the following?

surf(re_z, im_z, abs(f_of_z_result),'EdgeColor','none');

[Aisha Mohamed]

Thank you Chunru, your command plot the magnitude of this polynomial (|f(z)|).

but I meant,

how to plot the cosine of this function?

I really apriciate any help.

[Torsten]

The cosine of a complex-valued function is complex-valued. So you will have to tell us what you want to plot:

cos(abs(f_of_z_result)), abs(cos(f_of_z_result)), angle(cos(f_of_z_result)), cos(angle(f_of_z_result)),...

There are many possibilities.

[Aisha Mohamed]

Hi Torsten

Thank you very much for your answer. Because I study the behaviour of this function, could you please help me to plot all these possibilities?

I really appreciate your efforts.

[Torsten]

Just insert the expression you want in the surf command instead of abs(f_of_z_result).

[Aisha Mohamed]

Thanks Torsten so much, I really appriciate your efforts.

I will use all these commands to study my function.