Answer:
1.30 miles
Explanation:
The tangent relation is ...
tan(angle) = opposite/adjacent
The height of the surveyed point is the side of the right triangle that is opposite the angle of elevation. The horizontal distance to the surveyed point is the side of the triangle adjacent to the angle of elevation. So, we have ...
tan(18°) = height/(4 mi)
height = (4 mi)tan(18°) = 1.300 mi
The vertical change in elevation from the surveyor to the surveyed point is 1.300 miles.