where \({\phi }'\)=Apparent angle of dip, \(\phi \)= True angle of dip, \(\beta \)=Angle made by vertical plane with magnetic meridian.
\( \Rightarrow \tan {\phi }' = \frac{{\tan {{60}^o}}}{{\cos {{30}^o}}} = 2 \Rightarrow {\phi }' = {\tan ^{ - 1}}\left( 2 \right)\)