To find angle $ \beta $ use formula:
$$ \tan \left( \beta \right) = \dfrac{ b }{ a } $$After substituting $ b = 1 $ and $ a = 2 $ we have:
$$ \tan \left( \beta \right) = \dfrac{ 1 }{ 2 } $$ $$ \tan \left( \beta \right) = \frac{ 1 }{ 2 } $$ $$ \beta = \arctan\left( \frac{ 1 }{ 2 } \right) $$ $$ \beta = 26.5651^o $$