STEP 1: find angle $ \alpha $
To find angle $ \alpha $ use formula:
$$ \sin \left( \alpha \right) = \dfrac{ h }{ a } $$After substituting $h = 1.25\, \text{cm}$ and $a = 2.9\, \text{cm}$ we have:
$$ \sin \left( \alpha \right) = \dfrac{ 1.25\, \text{cm} }{ 2.9\, \text{cm} } $$ $$ \sin \left( \alpha \right) = 0.431 $$ $$ \alpha = \arcsin\left( 0.431 \right) $$ $$ \alpha = 25.5332^o $$STEP 2: find angle $ \beta $
To find angle $ \beta $ use formula:
$$ \alpha + \beta = 90^o $$After substituting $ \alpha = 25.5332^o $ we have:
$$ 25.5332^o + \beta = 90^o $$ $$ \beta = 90^o - 25.5332^o $$ $$ \beta = 64.4668^o $$