The sum of all possible value of \( \theta \in [0,2\pi] \), for which the system of equations:\( x\cos 3\theta-8y-12z=0 \)\( x\cos 2\theta+3y+3z=0 \)\( x+y+3z=0 \)has a non-trivial solution, is equal to:
\( \pi \)
\( 2\pi \)
\( 3\pi \)
\( 4\pi \)