To find hypotenuse $ c $ use formula:
$$ \cos \left( \beta \right) = \dfrac{ a }{ c } $$After substituting $ \beta = 16^o $ and $ a = 13 $ we have:
$$ \cos( 16^o ) = \dfrac{ 13 }{ c } $$ $$ 0.9613 = \dfrac{ 13 }{ c } $$ $$ c = \dfrac{ 13 }{ 0.9613 } $$ $$ c = 13.5239 $$