$(5$ POINTS$)$ Evaluate the following limits:

$($a$)\underset{x-1}{lim}\frac{x^2-x-2}{x+1}$

$($b$)\underset{x36}{lim}\frac{36-x}{6-\sqrt[\phantom{2}]{x}}$

$($c$)\underset{x0}{lim}\frac{sin(x)}{xcos(x)}$

HINT: Use the fact that $\underset{x0}{lim}\frac{sin(x)}{x}=1.$