## Multivariable Calculus, 7th Edition

$\Sigma^{\infty}_{n=0} \frac{\pi^{n}}{3^{n+1}} = \Sigma^{\infty}_{n=0} \frac{\pi^{n}}{3^{n} \times 3^{1}}$ $=\Sigma^{\infty}_{n=0} \frac{1}{3} (\frac{\pi}{3})^{n}$ $a=\frac{1}{3}$ and $r=\frac{\pi}{3} \gt 1$ Since $|r| \gt 1$ the given series is divergent.