1. Nov 28, 2011

### pcvt

and that is the exact question I need to to answer.

The problem is, I can only use an argument in real analysis.

I see the answer is sqrt(2), but I cannot get that answer.

I've tried a lot of little manipulations to get different geometric series but I can't seem to get it.

Thanks

2. Nov 28, 2011

### deluks917

What is the taylor series? What tests did you try? It might be easier to find the radius of convergence of 1/(1+x) about 1.

3. Nov 28, 2011

### pcvt

I don't see an easy formula for the nth derivative so I'm not sure how to proceed in that direction

4. Nov 28, 2011

### deluks917

I didn't do 1/(1+x^2) but there is nice form of the nth derivative of 1/(1+x)

5. Nov 28, 2011

### pcvt

Do you mean I can use that to get a taylor series for my function