x(t)=Φ(t)Φ−1(t0)x0+Φ(t)∫tt0Φ−1(s)f(s)ds \ Phi^ {-1} (s)\ mathbf {f} (s) &=\ left (\ begin {array} {cc...\boldsymbol{\mathbf{x}(t)=\Phi(t) \Phi^{-1}\left(t_{0}\right) \mathbf{x}_{0}+\Phi(t) \int_{t_{0}}^{t} \Phi^{-1}(s) \mathbf{f}(s) d s \label{2.74}} \ Phi^ {-1} (s)\ mathbf {f} (s) &=\ left (\ begin {array} {cc}\ cos s & -\ sin s\\ sin s &\ cos s\ end {array}\ right)\ left (\ begin {array} {c} 0\\ 2\ cos s\ end {array}\ right)\\ \ Phi (t)\ int_ {t_ {0}} ^ {t}\ Phi^ {-1} (s)\ mathbf {f} (s) d s &=\ left (\ begin {array} {c}
