Answer
$\dfrac{\sqrt3}{2}$
Work Step by Step
RECALL:
(1) $\sin{\theta} = \dfrac{\text{opposite side}}{\text{hypotenuse}}$
(2) $\tan{\theta} = \dfrac{\text{opposite side}}{\text{adjacent side}}$
(3) $\cos{\theta} = \dfrac{\text{adjacent side}}{\text{hypotenuse}}$
Use formula (3) above.
Use the 30-degree angle of the triangle on the right to obtain:
$\cos{30^o} = \dfrac{\sqrt3}{2}$
