2.10.100 Number Series

Condition: Explore the convergence of numerical rows: a) find out whether a positive series converges or diverges; b) find out whether the alternate series converges or diverges; If the row converges, set the nature of the convergence. a) \ (\ sum_ {n = 1}^{\ infty} \ frac {\ pi^{n}} {3^{n} \ cdot n^{3} \), b) \ (\ sum_ {n = 1}^\ infty} \ frac {\ sin n} {5^{n}} \).