\(\tan (30+\theta)=\frac{5+10}{5 \sqrt{3}}=\frac{1+2}{\sqrt{3}}\)
\(\frac{\tan \theta+\frac{1}{\sqrt{3}}}{1-\frac{1}{\sqrt{3}} \tan \theta}=\sqrt{3}\)
\(\sqrt{3} \tan \theta+1=3-\sqrt{3} \tan \theta\)
\(2 \sqrt{3} \tan \theta=2\)
\(\tan \theta=\frac{1}{\sqrt{3}}\)
\(\theta=30^{\circ}\)