STEP 1: find angle $ \alpha $
To find angle $ \alpha $ use formula:
$$ \alpha + \beta = 90^o $$After substituting $ \beta = 60^o $ we have:
$$ \alpha + 60^o = 90^o $$ $$ \alpha = 90^o - 60^o $$ $$ \alpha = 30^o $$STEP 2: find height $ h $
To find height $ h $ use formula:
$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ h }{ d_1 } $$After substituting $ \alpha = 15^o $ and $ d_1 = 60 $ we have:
$$ \sin \left( \frac{ 30^o }{ 2 } \right) = \dfrac{ h }{ 60 } $$ $$ \sin( 15^o ) = \dfrac{ h }{ 60 } $$ $$ 0.2588 = \dfrac{ h }{ 60 } $$$$ h = 0.2588 \cdot 60 $$$$ h = 15.5291 $$