Qual o valor de $\cos 22,5^o + \sin 22,5^o$?

$\cos \dfrac{\pi}{8} + \sin \dfrac{\pi}{8} = \cos \dfrac{\pi}{8} + \cos \dfrac{3\pi}{8} = 2\left(\cos \dfrac{\pi}{4}\right)\left(\cos \dfrac{\pi}{8}\right) = $

$= \sqrt{2}\sqrt{\dfrac{1 + \cos \dfrac{\pi}{4}}{2}} = \fbox{$\sqrt{1 + \dfrac{\sqrt{2}}{2}}$}$