Amplitude Modulation Concepts
I don't understand I in your formula. 

Normally (traditionally) AM is: -

y(t) = [A + M cos(ωm t + φ)] . sin(ωc t) 

where 


y(t) is the final modulated signal
M is the amplitude of the modulating cosine (or sine to answer your
question)
A is the amplitude of the carrier sine (or cosine to reinforce the
answer!!)
φ is the phase displacement of the modulating sinewave but is
irrelevant all but mathematically
ωm and ωc are the frequencies of modulation and carrier.


Maybe I just don't recognize your formula but the answer is, like Jim Dearden implies swap them up or use the same because carrier and modulator are not going to be the same frequency when dealing with AM.