Answer:
272.17 ft
Explanation:
Since the angle of depression of the sighting equals the angle of elevation of the lighthouse from the boat, using trigonometric ratios,
tanθ = x/d where θ = angle of sighting, x = height of lighthouse =55 ft and d = distance of boat from lighthouse at sighting
So, d = x/tanθ
when θ = 8.1°, for the first sighting,
d₁ = 55/tan8.1 = 386.45 ft
when θ = 25.7°, for the second sighting,
d₂ = 55/tan8.1 = 114.28 ft
The distance the boat traveled between the two sightings is thus d₁ - d₂ = 386.45 ft - 114.28 ft = 272.17 ft