A time-invariant system
For any input signal x(t), a system yelids y(t). Now, suppose input signal shifted t0, x(t-t0). Then output signal also shifted t0, y(t-t0). Then we can say a system is time-invariant.
Example of a tume-invariant system
x(t) = $ e^t $
Output signal y(t) can be $ 10e^t $ by system
Prove.
1. $ e^t $ is changed to $ e^{t-t0} $ by time delay.
$ e^(t-t0) -> 10e^(t-t0) $ by system.
2. $ e^t -> 10e^t $ by system.
$ 10e^t -> 10e^{t-t0} $
The output signals are same. Then we can say that the system is time-invariant.