A Plane Flying at an Altitude of a Miles Above $a = 8$

Multiple Choice

A plane flying at an altitude of a miles above a radar antenna will pass directly over the radar antenna (see figure) .Let d be the ground distance from the antenna to the point directly under the plane and let x be the angle of elevation to the plane from the antenna. $a = 8$ .
(d is positive as the plane approaches the antenna.)
Write d as a function of x.

A) d = 8 csc x
B) d = 8 cot x
C) d = 8 cos x
D) d = 8 tan x
E) d = 8 sin x