EXERCISE $3\mathrm{.}2$

If the two sinusoids being added were to have nonzero phases, that is$,$

x$($t$)=$ cos$(2$ fit $+41)+$ cos$(2$ f$2$t $+42)$

the frequencies, f$,$ and fa$,$ would remain the same, but the phases, and c$,$ would change.

x$($t$)=2$ cos$(2$$$t $+$a$)$ cos$(2$ fet $+$ c$)$

Determine the phases needed in the product representation.