The series is: $\displaystyle \sum (-\pi ^2)^n/(2n)!9^n$
and the instruction are to "sum the series." What is expected of me here? I am supposed to make an estimation? Treat it as an alternating series? I'm not sure where to start
The series is: $\displaystyle \sum (-\pi ^2)^n/(2n)!9^n$
and the instruction are to "sum the series." What is expected of me here? I am supposed to make an estimation? Treat it as an alternating series? I'm not sure where to start
you just said that $\displaystyle \sum_{n = 0}^{\infty} \frac{(-1)^n x^{2n}}{(2n)!} = \cos{x}$ , right?
LOOK at the your series again ... what is "x" in that series?
$\displaystyle \sum_{n = 0}^{\infty} \frac{(-1)^n \textcolor{red}{\pi}^{2n}}{(2n)! \cdot \textcolor{red}{3}^{2n}}$