we all know that:
lim
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.
No comments:
Post a Comment