At 11/29/09 12:22 PM, trig1 wrote:
And if anyone can explain why 1+1+1+1+... = -1/2 and not infinity I would appreciate it.
I have no idea where you could learn more about subjects like this.
Here's the thing: your series does not converge, it's divergeant. The approach you're taking results in saying that the partial sums in all divergeant series tend towards +inf or -inf, but that's not incredibly useful, is it? Instead, what you read about is the Cesàro summation. Note that not all divergeant series tend towards infinity. Take for example 1 - 1 + 1 - 1 ... It's obviously bound to [0, 1], yet it doesn't converge towards anything.
as n tends towards +inf, so does 1+1+1... n times. But so does 1+2+3 n times, k^1 + k^2 + k^3 n times, etc, yet they are all different series and therefore, evaluating the convergence of a divergeant series is pointless as it doesn't say anything about the series itself.
Anyway have a look at it for yourself. Here's a useful link. You can use wikipedia if you're curious about something, but I'd recommend reading official documents like university papers etc. Also, you'll see that much of the information on wikipedia is basically copy-pasted from this paper.
Gust, using seemingly complicated words doesn't make your answers right. Your post didn't make much sense. Divergeant series don't have a definite value as n->inf by definition (which is pretty much the answer to trig's question) it DOES tend towards infinity but that's not what Cesaro sums are about.