Amplitude Modulation Equation (sine or cosine)

Question

I got an exam tomorrow and I'm still confused with something. I'm sure most people are familiar with the general equation of Amplitude Modulation.

AM(t) = (Ac+m(t))cos ωc t

I found that there is another variant of which cosine is changed with sine.

AM(t) = (Ac+m(t))sin ωc t

And this also applied to both c(t) and m(t) somehow. My thought is that both can be used and it just depends on the waveform/equation given in questions. In my class we used only the one with cosine, so I never get the explanation for this.

Answer 1

You are right, both can be used. The useful information you want to transmit through amplitude modulation is contained within the (Ac+m(t)) expression. So the fact that you use a sine or a cosine doesn't really matter in the end.