\(x_1=A\cos\left(2\pi f_1t\right)\)
\(x_2=A\cos\left(2\pi f_2t\right)\)
\(x=x_1+x_2=2A\color{red}{\cos\left(2\pi f_{\mathrm{avg}}t\right)}\color{green}{\cos\left(\pi f_\mathrm{B}t\right)}\)
\(f_\mathrm{B}=\left|f_1-f_2\right|\)
\(f_1=\)
\(f_2=\)
\(A=\)
\(x_1\) \(x_2\) \(x=x_1+x_2\)