[tex]\large\boxed{\begin{array}{l}\rm a)~\sf\dfrac{\pi}{4}+\dfrac{\pi}{3}+\dfrac{\pi}{2}=\dfrac{3\pi+4\pi+6\pi}{12}=\dfrac{13\pi}{12}\\\\\rm b)~\sf\dfrac{17\pi}{3}-\dfrac{\pi}{4}-\dfrac{5\pi}{2}=\dfrac{68\pi-3\pi-30\pi}{12}=\dfrac{35\pi}{12}\end{array}}[/tex]
