Friday, October 14, 2016

calculus - Limit $lim_{x to 1} frac{log{x}}{x-1}$ without L'Hôpital




I was wondering if it's possible to identify this limit without using L'Hôpital's Rule:

$$\lim_{x \to 1} \frac{\log{x}}{x-1}$$


Answer



In THIS ANSWER and THIS ONE I showed, without the use of calculus, that the logarithm function satisfies the inequalities



$$\frac{x-1}{x}\le \log(x)\le x-1$$



Therefore, we can write for $x>1$



$$\frac1x \le \frac{\log(x)}{x-1}\le 1$$




and for $x<1$



$$1 \le \frac{\log(x)}{x-1}\le \frac1x$$



whereupon applying the squeeze theorem yields the result $1$.


No comments:

Post a Comment

analysis - Injection, making bijection

I have injection $f \colon A \rightarrow B$ and I want to get bijection. Can I just resting codomain to $f(A)$? I know that every function i...