(b)
$f\left( \frac{\pi}{2} + x \right) = \left| \sin\left( \frac{\pi}{2} + x \right) \right| + \left| \cos\left( \frac{\pi}{2} + x \right) \right|$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \left| \cos x \right| + |\sin x|$ for all $x$.
Hence, $f(x)$ is periodic with period $\frac{\pi}{2}$.