Using Mupad to add sinusoids of same frequency

Hi,

I'm attempting to combine the sum of two sinusoids with the same frequency into one term like A*cos(omega*t+phiA) + B*cos(omega*t + phiB) = C*cos(omega*t + phiC) in Mupad.

I found no solution to handle this automatically. Anybody an idea how to solve this problem?

Thank you.

Kind regards, Mathias