 satisfied when we choose the value
                \[
                \arg\left(z_2\right) =\theta_2 + 2(n-k)\pi.
                \]
                The verification when values of 
                $\arg\left(z_1z_2\right)$ and $\arg\left(z_2\right)$ are specified follows by symmetry.
            </p>

            <p>
                Statement (\ref{arg-product}) is sometimes valid when $\arg$ is replaced 
                everywhere by $\Arg.$ However, as the following example illustrates, that is not 
   