Evaluate the following limits:
$\lim _{x \rightarrow 0} \frac{\tan x-\sin x}{\sin ^{3} x}$
To Find: Limits
NOTE: First Check the form of imit. Used this method if the limit is satisfying any one from 7 indeterminate form.
In this Case, indeterminate Form is $\frac{0}{0}$
NOTE $: \tan x-\sin x=\frac{\sin x}{\cos x}-\sin x=\frac{\sin x-\sin x \cos x}{\cos x}=\sin x\left(\frac{1-\cos x}{\cos x}\right)$
$\lim _{x \rightarrow 0} \frac{\tan x-\sin x}{\sin ^{2} x}=\lim _{x \rightarrow 0} \frac{\frac{1-\cos x}{\cos x}}{\sin ^{2} x}=\lim _{x \rightarrow 0} \frac{1-\cos x}{\sin ^{2} x \cos x}$
Divide numerator and denominator by $x^{2}$,
$=\lim _{x \rightarrow 0} \frac{\frac{1-\cos x}{x^{2}}}{\frac{\sin ^{2} x \cos x}{x^{2}}}$
Formula used: $\lim _{x \rightarrow 0} \frac{1-\cos x}{x^{2}}=1 / 2$ and $\lim _{x \rightarrow 0} \frac{\sin x}{x}=1$ or we can used $L$ hospital Rule,
So, by using the above formula, we have
$\lim _{x \rightarrow 0} \frac{\frac{1-\cos x}{x^{2}}}{\frac{\sin ^{2} x \cos x}{x^{2}}}=\frac{\frac{1}{2}}{1}=\frac{1}{2}$
Therefore, $\lim _{x \rightarrow 0} \frac{\tan x-\sin x}{\sin ^{3} x}=\frac{1}{2}$