Question

approximate the sum of............ to four decimal places

Answer 1

\[\sum_{n = 1}^{\infty} (-1)^{n+1} / n! \]

Answer 2

Just take those summands where \(n! < 10^5\)

Answer 3

1 +( (-1)^3)/2 +( (-1)^4) /6 + -1/2
1 -1/2 + 1/6 -1/24 + 1/120 - 1/720 + 1/..

Answer 4

-comes to 0.6321 by my reckoning