Question

If a continuous time signal x(t) = cos$\left(2\pi t\right)$ is sampled at 4 Hz the value of the discrete time sequence x(n) = 5 is

Answer 1

$x\left(n{T}_s\right)=cos2\pi \cdot \frac{n}{4}=cos\frac{\pi }{2}n=x\left(n\right)$

$x\left(n\right){\mid }_{n=5}=cos\frac{5\pi }{2}=0$