Closed form expression for $\sum_{i=1}^n a_i \cos(wt_i + \phi)$

Question

Is there a closed-form solution for \begin{align} \sum_{i=1}^n a_i \cos(wt_i + \phi) \end{align}

We can recursively use: $a\cos(x) + b\sin(x)$ as $R \cos(x − α)$ where $R = \sqrt{a^2 + b^2}$ and $\tan{\alpha} = \frac{b}{a}$.

But is there a neat solution for the above sum?