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Question 5.35

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TZ
leumasicOfficial

3 months ago

We have

α=limx0sinxx.\alpha=\lim_{x\to 0}\frac{\sin x}{x}.

i)

limxsinxx=limx0+sin(1/x)1/x=limx0sin(1/x)1/x=1α,\begin{align*} \lim_{x\to\infty}\frac{\sin x}{x} &=\lim_{x\to 0^+}\frac{\sin(1/x)}{1/x} \\ &=\lim_{x\to 0}\frac{\sin(1/x)}{1/x} \\ &=\frac{1}{\alpha}, \end{align*}

assuming α0\alpha\neq 0.

ii)

limxxsin(1x)=limx0+1xsinx=limx0sinxx=α.\begin{align*} \lim_{x\to\infty}x\sin\left(\frac{1}{x}\right) &=\lim_{x\to 0^+}\frac{1}{x}\sin x \\ &=\lim_{x\to 0}\frac{\sin x}{x} \\ &=\alpha. \end{align*}
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Q 5.35

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Q 5.35