Answer:
0.3 miles
Step-by-step explanation:
Using Trigonometry ;
Height, h = 2 miles
First sighting :
Horizontal distance h1 ;
h1 = 2tanθ
θ = 11°
h1 = 2 * 0.1943803
h1 = 0.3887606 miles
Second sighting ;
Horizontal distance h2 ;
h2 = 2tanθ
θ = 18°
h2 = 2 * 0.3249196
h2 = 0.6498393 miles
Horizontal difference :
0.6498393 miles - 0.3887606 miles
= 0.2610787 miles
= 0.3 miles