Chapter 9.7, Problem 16E

In Problems 11-16, use the variation of parameters formula (11) to find a general solution of the system $x^{\prime }\left(t\right)=Ax\left(t\right)+f\left(t\right)$, where A and $f\left(t\right)$ are given.

$A=\left[\begin{array}{cc}0& 1\\ -1& 0\end{array}\right],f\left(t\right)=\left[\begin{array}{c}8\sin t\\ 0\end{array}\right]$