$\text{ The true set of real values of "a" such that the point }\mathrm{M}(a,\sin a)\text{ lies inside the triangle }$

$\text{ formed by the lines }x-2y+2=0,x+y=0\text{ and }x-y-\pi =0\text{ is }$

• A

  $\left(0,\pi \right)$

• B

  $\left(\frac{\pi }{3},\frac{\pi }{2}\right)$

• C

  $\left(0,\frac{\pi }{6}\right)\cup \left(\frac{\pi }{3},\frac{\pi }{2}\right)$

• D

  $\left(\frac{\pi }{2},\pi \right)\cup \left(\frac{2\pi }{3},2\pi \right)$