# Is the limit also infinity?

1. Feb 4, 2006

### Gamma

Hi,

What is the limit of
$$ln(\frac{1+1/ \sqrt(1+1/R)}{1-1/ \sqrt(1+1/R})$$

as R reaches infinity.

(latex did not show it very well. But the numerator is same as denominator except there is a + sign instead of a - sign.

As R reaches infinity the argument of the ln reaches infinity. Is the limit also infinity?

Thank You.

Gamma.

Last edited by a moderator: Feb 5, 2006
2. Feb 5, 2006

### VietDao29

If your LaTeX image is big, don't use [ itex ], use [ tex ] instead.
So do you mean:
$$\lim_{R \rightarrow \infty} \ln \left( \frac{1 + \frac{1}{\sqrt{1 + R}}}{1 - \frac{1}{\sqrt{1 + R}}} \right)$$? Or what?
If you mean that, then if $$R \rightarrow \infty$$, then $$\sqrt{1 + R} \rightarrow \ ?$$, $$\frac{1}{\sqrt{1 + R}} \rightarrow \ ?$$, $$1 \pm \frac{1}{\sqrt{1 + R}} \rightarrow \ ?$$.
Can you go from here? :)

3. Feb 5, 2006

### HallsofIvy

Staff Emeritus
Gamma, I've taken the liberty of editing your Latex by changing "itex" to "tex". "itex" doesn't work well with complex fractions.

As VietDao29 told you- the argument inside the ln does NOT go to infinity. It should be sufficient to see what happens to 1/R as R goes to infinity.