To find angle $ \alpha $ use formula:
$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ d_2 }{ d_1 } $$After substituting $ d_2 = 2 $ and $ d_1 = 5 $ we have:
$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ 2 }{ 5 } $$ $$ \sin \left( \frac{ \alpha }{ 2 } \right) = \frac{ 2 }{ 5 } $$ $$ \frac{ \alpha }{ 2 } = \arcsin\left( \frac{ 2 }{ 5 } \right) $$ $$ \frac{ \alpha }{ 2 } = 23.5782^o $$$$ \alpha = 23.5782^o \cdot 2 $$$$ \alpha = 47.1564^o $$