Answer
$0,1.911,\pi,4.373$
Work Step by Step
1. $-3cos(\frac{\pi}{2}-\theta)=tan\theta\Longrightarrow -3sin(\theta)=\frac{sin\theta}{cos\theta}\Longrightarrow sin(\theta)=0\ or\ cos\theta-=\frac{1}{3}$
2. For $sin\theta=0$, we have $\theta=k\pi$
3. For $cos\theta-=\frac{1}{3}$, we have $\theta=2k\pi+1.911$ or $\theta=2k\pi+4.373$
4. Within $[0,2\pi)$, we have $\theta=0,1.911,\pi,4.373$
