1. The problem statement, all variables and given/known data Using trig identities from a calculus book or other, write out the results to the following modulations. State which frequencies exist in the signal s(t). 2. Relevant equations a) s(t) = Acos(2∏f₁t) * Bcos(2∏f₂t) 3. The attempt at a solution cos(s) * cos(t) = cos (s + t)/2 + cos (s – t)/2 s(t) = ((AB)/2)*(cos(2∏t(f1 + f2)) + cos(2∏t(f1 - f2))) What I don't quite understand is the part that asks to state which frequencies exist in the signal. I understand that in modulation, half of the signal is shifted to the right by f2, then the other half of the signal is shifted to the left by f2. Which would make the answers f2 and -f2. According to the answer it should be f1, f2, |f2-f1|, f1+f2.