An LTI system is "initially relaxed" or "at rest" if all its initial conditions are zero before an input is applied. This means there is no stored energy in the system.
A consequence of being initially relaxed is that if the input to the system is zero for all time (\(x(t)=0\) or \(x[n]=0\)), then the output will also be zero for all time (\(y(t)=0\) or \(y[n]=0\)). This is known as the zero-input zero-output (ZIZO) property for a system at rest.
If a zero input produces a non-zero output, it indicates the presence of non-zero initial conditions.
\[ \boxed{\text{Zero input produces zero output}} \]
Signals and their Fourier Transforms are given in the table below. Match LIST-I with LIST-II and choose the correct answer.
| LIST-I | LIST-II |
|---|---|
| A. \( e^{-at}u(t), a>0 \) | I. \( \pi[\delta(\omega - \omega_0) + \delta(\omega + \omega_0)] \) |
| B. \( \cos \omega_0 t \) | II. \( \frac{1}{j\omega + a} \) |
| C. \( \sin \omega_0 t \) | III. \( \frac{1}{(j\omega + a)^2} \) |
| D. \( te^{-at}u(t), a>0 \) | IV. \( -j\pi[\delta(\omega - \omega_0) - \delta(\omega + \omega_0)] \) |