we all know that:
$\lim\limits_{x\to0}\frac{\sin x}x=1$
so what is the negative
$\lim\limits_{x\to0}-\frac{\sin x}x=$?
i am trying to prove what about $\lim\limits_{x\to0}\frac{x^2\sin \frac 1x}{\sin^2 x}$
i got to $\frac{-x^2}{\sin^2 x} \le $ $\frac{x^2\sin \frac 1x}{\sin^2 x}\le$$\frac{x^2}{\sin^2 x}$
and $\lim\limits_{x\to0}\frac{x^2}{\sin^2 x}= \lim\limits_{x\to0}\frac{\sin x}x\lim\limits_{x\to0}\frac{\sin x}x= 1\times1=1 $
and$\lim\limits_{x\to0}-\frac{x^2}{\sin^2 x}= \lim\limits_{x\to0}\frac{\sin x}x\lim\limits_{x\to0}-\frac{\sin x}x=?$
Answer
Simply put,
$$\lim_{x\to a} (Af(x))=A\lim_{x\to a} f(x),\text{ where $A$ is a constant.}$$
So let $A=-1$ in your expression.
Edit: Let me generalize:
If $\lim_{x\to a}f(x),\lim_{x\to a}g(x)$ exist, then $\lim_{x\to a}(f(x)g(x))$ exists. So, let $g(x)=\dfrac{\sin x}{x},f(x)=-1$.
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