Equation of motion for a vibration system with one degree of freedom/1自由度振動系の運動方程式
\begin{align} m\ddot{x}(t) + c\dot{x}(t)+kx(t)=f(t) \end{align} \begin{align} m\ddot{x} + c\dot{x}+kx=f \end{align}Definition of Fourie transform/フーリエ変換の定義
\begin{align} X(\omega) = \int_{-\infty}^{+\infty}x(t)e^{-i\omega t}dt \end{align} \begin{align} X(f) = \int_{-\infty}^{+\infty}x(t)e^{-i2\pi ft}dt \end{align}