Check the picture below.
[tex]tan(\theta )=\cfrac{\stackrel{opposite}{3}}{\underset{adjacent}{28}}\implies tan^{-1}[tan(\theta )]=tan^{-1}\left( \cfrac{3}{28} \right) \\\\\\ \theta =tan^{-1}\left( \cfrac{3}{28} \right)\implies \theta \approx 6.12^o[/tex]
Make sure your calculator is in Degree mode.
