# How do you use a power series to find the exact value of the sum of the series 1-pi^2/(2!)+pi^4/(4!) +pi^6/(6!) + … ?

1-x^2/{2!}+{x^4}/{4!}-x^6/{6!}+cdots=cosx,
1-pi^2/{2!}+pi^4/{4!}-pi^6/{6!}+cdots=cos(pi)=-1