## Calculus 8th Edition

Given: $a_{n}=cos(n\pi/2)$ A sequence is said to be converged if and only if $\lim\limits_{n \to \infty}a_{n}$ is a finite constant. Now, $\lim\limits_{n \to \infty}a_{n}=\lim\limits_{n \to \infty}cos(n\pi/2)$ In this case, $a_{n}=[0,-1,0,1,0,-1,0,1,...]$ This implies that the sequence has no limit. Hence, the given sequence is divergent.