math (trig)
posted by haley .
from the top of a bridge over the burlington canal, maria looks down at a sailboat at an angle of depression 15 degrees.the bridge is 18m above the water. calculate the horizontal distance from the bridge to the sailboat

You are looking at a right triangle of which one angle is 15°, the opposite side is 18m (vertical).
From the definition of tangent,
tan(θ)=opposite (18m) / adjacent (H)
where H is the horizontal distance required.
Solve for H since θ and opposite are known.