Answer
$0$
Work Step by Step
Step 1. Rewrite the equation $3-3cos\theta=1-cos^2\theta \longrightarrow cos^2\theta-3cos\theta+2 \longrightarrow (cos\theta-1)(cos\theta-2)=0$. Thus $cos\theta=1$ or $cos\theta=2$.
Step 2. For $cos\theta=1$, we have $\theta=0$
Step 3. For $cos\theta=2$, we have $\theta=none$
