<image>As shown in the figure, in the coordinate plane $$xOy$$, starting at the $$Ox$$ axis, two acute angles $$α$$ and $$β$$ are drawn. Their terminal sides intersect the unit circle at points $$A$$ and $$B$$ respectively. It is known that the x-coordinates of points $$A$$ and $$B$$ are $$ \dfrac { \sqrt {2}}{10}$$ and $$ \dfrac {2 \sqrt {5}}{5}$$ respectively. Find the value of $$\tan (α+β)$$ = ______ .