Sunday 6 January 2013

limits - Use of L'hopital's rule



Define $f:\mathbb{N} \to \mathbb{R}$ by $f(n)=\frac{sin (\frac{n\pi}{4})}{n}.$



May I know if we can use L'hopital's rule to evaluate $\lim_{n \to 0} f(n)$ ? If not, how can we evaluate the limit without the use of series?



Thank you.


Answer



There is no such ting as $\lim_{n\to0}f(n)$ if $f$ is only defined on $\mathbb N$.



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