144. Find $\lim _{x \rightarrow 0} \frac{\sin k x}{\sin l x}$.
Solution. We have

$$
\lim _{x \rightarrow 0} \frac{\sin k x}{\sin l x}=\lim _{x \rightarrow 0} \frac{\frac{\sin k x}{x}}{\frac{\sin l x}{x}}=\frac{\lim _{x \rightarrow 0} \frac{\sin k x}{x}}{\lim _{x \rightarrow 0} \frac{\sin l x}{x}}=\frac{k}{l}
$$

Here we divided the numerator and the denominator of the fraction by $x$ (this can be done since $x \rightarrow 0$, but $x \neq 0$), and then used the result from the previous example.