For right triangles, use SOH CAH TOA.
Given angle is 27, given sides are 'x' and 20.
Which sides are given, opposite, adjacent, or hypotenuse?
opposite is across from angle(27) -----> unknown
adjacent is leg next to or touching the angle(27) -----> 'x'
hypotenuse is side across from right angle -----> 20
which trig ratio uses adjacent and hypotenuse?
CAH has both A for adjacent and H for hypotenuse.
Therefore use the cosine ratio.
[tex]cos(27) = \frac{x}{20} \\ \\ x = 20*cos(27) \\ \\ x = 17.8[/tex]
