Answer
(a) $$\lim_{x\to0}\frac{x\sin x}{2-2\cos x}=1$$
(b) As $x\to0$, all of the three graphs approach $y=1$, squeezing together as they go.
Work Step by Step
(a) - Calculate $\lim_{x\to0}(1-\frac{x^2}{6})$ and $\lim_{x\to0}(1)$
$\lim_{x\to0}\Big(1-\frac{x^2}{6}\Big)=1-\frac{0^2}{6}=1-0=1$
$\lim_{x\to0}1=1$
So, $\lim_{x\to0}(1-\frac{x^2}{6})=\lim_{x\to0}1=1$
- Yet $1-\frac{x^2}{6}\le \frac{x\sin x}{2-2\cos x}\le 1$ for all $x$ close to $0$
Therefore, applying the Sandwich Theorem, we can conclude that $$\lim_{x\to0}\frac{x\sin x}{2-2\cos x}=1$$
A note here is that the inequality does not have to hold for $x=0$ though, if it already holds for all values of $x$ close to $0$ for the simple reason that $\lim_{x\to0}$ accounts for only the values of $x$ close to $0$ and does not account for $0$.
(b) The graph is shown below.
As $x\to0$, all of the three graphs approach $y=1$, squeezing together as they go.
