ANSWER
[tex]\begin{equation*} 10.64\text{ }Hz \end{equation*}[/tex]EXPLANATION
We want to find the frequency of the Voltage.
From the equation of the voltage, the coefficient of t represents the angular frequency. This implies that the angular frequency is:
[tex]\omega=66.883[/tex]The angular frequency is related to the frequency as follows:
[tex]\begin{gathered} \omega=2\pi f \\ \\ f=\frac{\omega}{2\pi} \end{gathered}[/tex]Therefore, the frequency of the voltage is:
[tex]\begin{gathered} f=\frac{66.883}{2\pi} \\ \\ f=10.64\text{ }Hz \end{gathered}[/tex]That is the answer.