Sunday, 6 March 2016

calculus - What is the $lim_limits{nto infty}frac{sinfrac{1}{n}}{frac{1}{n}}$




$$\lim_\limits{n\to \infty}\frac{\sin\frac{1}{n}}{\frac{1}{n}}$$



How am I supposed to know this equals 1?



I could sub $x= \frac{1}{n}$ to get



$$\lim_\limits{x\to \infty}\frac{\sin(x)}{x} $$



Using L'Hopital's I'd get:




$$\lim_\limits{x\to \infty}\frac{\cos(x)}{1} $$



But, $\cos(x)$ just cycles between $-1$ and $1$, so how can the limit be $1$ ?


Answer



HINT:



If $x=\frac{1}{n}$, then as $n\to\infty$, $x\to 0^+$



So the limit becomes:

$$\lim_\limits{x\to 0^+}\frac{\sin x}{x}$$


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