STEP 1: find angle $ \alpha $
To find angle $ \alpha $ use formula:
$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ d_2 }{ d_1 } $$After substituting $d_2 = 15\, \text{cm}$ and $d_1 = 40\, \text{cm}$ we have:
$$ \sin \left( \frac{ \alpha }{ 2 } \right) = \dfrac{ 15\, \text{cm} }{ 40\, \text{cm} } $$ $$ \sin \left( \frac{ \alpha }{ 2 } \right) = \frac{ 3 }{ 8 } $$ $$ \frac{ \alpha }{ 2 } = \arcsin\left( \frac{ 3 }{ 8 } \right) $$ $$ \frac{ \alpha }{ 2 } = 22.0243^o $$$$ \alpha = 22.0243^o \cdot 2 $$$$ \alpha = 44.0486^o $$STEP 2: find angle $ \beta $
To find angle $ \beta $ use formula:
$$ \alpha + \beta = 90^o $$After substituting $ \alpha = 44.0486^o $ we have:
$$ 44.0486^o + \beta = 90^o $$ $$ \beta = 90^o - 44.0486^o $$ $$ \beta = 45.9514^o $$