Answer
$a \approx 18$ cm
Work Step by Step
RECALL:
(1) $\sin{\theta} = \dfrac{\text{opposite side}}{\text{hypotenuse}}$
(2) $\cos{\theta} = \dfrac{\text{adjacent side}}{\text{hypotenuse}}$
(3) $\tan{\theta} = \dfrac{\text{opposite side}}{\text{adjacent side}}$
Use (3) above to obtain:
$\tan{61^o}=\dfrac{a}{10}
\\a=10(\tan{61^o})$
Use a calculator in DEG mode to obtain
$\\a=18.04047755
\\a \approx 18$ cm
