\(2\sqrt{3+\sqrt{5-\sqrt{13+4\sqrt{3}}}}=2\sqrt{3+\sqrt{5-\sqrt{12+4\sqrt{3}+1}}}\)
\(=2\sqrt{3+\sqrt{5-\sqrt{\left(2\sqrt{3}+1\right)^2}}}\)
\(=2\sqrt{3+\sqrt{5-2\sqrt{3}-1}}\)
\(=2\sqrt{3+\sqrt{3-2\sqrt{3}+1}}\)
\(=2\sqrt{3+\sqrt{3}-1}=2\sqrt{2+\sqrt{3}}\)