Right-hand limit, Left-hand limit

Exercise

1.
Find the limit of the follwing functions.D
(a)
$\displaystyle{\lim_{x \rightarrow 0}\frac{1}{x}}$
(b)
$\displaystyle{\lim_{x \rightarrow 0}\frac{1}{x^{2}}}$
(c)
$\displaystyle{\lim_{x \rightarrow 0+}\frac{\vert x\vert}{\sqrt{a+x} - \sqrt{a-x}}}$
(d)
$\displaystyle{\lim_{x \rightarrow 0-}\frac{x}{\sqrt{1-\cos{x}}}}$
(e)
$\displaystyle{\lim_{x \rightarrow \infty}\cos{\frac{1}{x}}}$
(f)
$\displaystyle{\lim_{x \rightarrow \infty}\frac{\sin{x}}{x}}$
(g)
$\displaystyle{\lim_{x \rightarrow 0+}\cos{\frac{1}{x}}}$