Question

The picture shows a barn door: A barn door has two parallel bars. A support AB of length 6 feet runs across the diagonal between the two parallel bars. The angle made by the diagonal with the parallel bar on top is 60 degrees. What is the length of the bar AC?
 a.  6 sin 60°
b.  6 cos 60°
c. 6/cos60
d. 6/tan60

Answer 1

Cosine is the ratio adjacent over hypotenuse.

The hypotenuse is the diagonal of 6 ft.

The adjacent side of the 60 degree angle is AC.

Therefore:
$cos 60 = \frac{AC}{6} \\ \\ AC = 6 cos 60$