Sum of 2 EM Waves w/ Same Phase & Amp but Diff Freq

[fluidistic]

Homework Statement

Describe the sum of two EM waves that have the same initial phase and same amplitude but different frequencies such that \omega _1 >> \omega _2.

Homework Equations

E=E_0 \cos (kx -\omega t + \alpha).

The Attempt at a Solution

I summed them up and reached, after an approximation, that E_1+E_2 \approx 2 E_0 \cos \left (kx -\frac{\omega _1t}{2} + \alpha \right ) \cos \left ( \frac{\omega _ 1 t}{2} \right ). I don't know how to simplify further. It seems that the amplitude is the sum of both amplitudes and I'm not sure yet what is the frequency. It should be almost \omega _1, intuitively. I just don't know how to show it.
Any help is appreciated.

 

[physicsworks]

Did you consider the fact that
k=\frac{\omega}{c}
and that's why k is different for the two plane waves with two different frequencies?

 

[fluidistic]

Did you consider the fact that
k=\frac{\omega}{c}
and that's why k is different for the two plane waves with two different frequencies?

Thanks, actually I didn't consider this. I will redo the exercise.