Let A={θ ∈[0,2 π]: 1+10 Re ((2 cos θ+i sin θ)/(cos θ-3 i sin θ))=0}. Then Σ_θ ∈ A θ^2 is equal to

Let $\displaystyle A=\left\{\theta \in[0,2 \pi]: 1+10 \operatorname{Re}\left(\frac{2 \cos \theta+i \sin \theta}{\cos \theta-3 i \sin \theta}\right)=0\right\}$. Then $\displaystyle \sum_{\theta \in \mathrm{A}} \theta^2$ is equal to