(a) Show that the function $f(x) = \begin{cases} \frac{\cos x}{-x+\frac{\pi}{2}}, & x \neq \frac{\pi}{2} \\ 1, & x = \frac{\pi}{2} \end{cases}$ is continuous at $x = \frac{\pi}{2}$. OR (b) Find whether the function $f(x) = \begin{cases} x-1, & x < 2 \\ 2x-3, & x \geq 2 \end{cases}$ at $x = 2$ is differentiable or not.