\(\sqrt{10+\sqrt{2}-\sqrt{2+\sqrt{9+4\sqrt{2}}}}=\sqrt{10+\sqrt{2}-\sqrt{2+\sqrt{8+2.2\sqrt{2}+1}}}\)
\(=\sqrt{10+\sqrt{2}-\sqrt{2+\sqrt{\left(2\sqrt{2}+1\right)^2}}}\)
\(=\sqrt{10+\sqrt{2}-\sqrt{2+2\sqrt{2}+1}}\)
\(=\sqrt{10+\sqrt{2}-\sqrt{\left(\sqrt{2}+1\right)^2}}\)
\(=\sqrt{10+\sqrt{2}-\sqrt{2}-1}=\sqrt{9}=3\)