We can draw the following right triangle:
since, we have a right triangle, we can apply Pythagorean theorem:
[tex](\sqrt[]{2})^2+(\sqrt[]{2})^2=z^2[/tex]which gives
[tex]\begin{gathered} 2+2=z^2 \\ 4=z^2 \\ z=\sqrt[]{4} \\ z=2 \end{gathered}[/tex]therefore, the missing side z is equal to 2.