$$\sqrt { 4 + \sqrt { 10 + 2 \sqrt { 5 } } } + \sqrt { 4 - \sqrt { 10 + 2 \sqrt { 5 } } }$$
$\sqrt{\sqrt{2\left(\sqrt{5}+5\right)}+4}+\sqrt{-\sqrt{2\left(\sqrt{5}+5\right)}+4}\approx 3.236067977$
