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

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: $acos(x) + bsin(x)$ 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?