In [1, p. 62 exercise 3.18] we are asked to find the temporal autocorrelation function for the real sinusoidal random process of Problem [1, p. 62 exercise 3.16]:
 $\hat{r}_{xx}[k]=\frac{1}{2M+1}\sum\limits_{n=-M}^{M}x[n]x[n+k]$

as $M\rightarrow \infty$. As a second step we are asked to determine if the random process autocorrelation ergodic. read the conclusion >