Answer:
arc DB length = 14π feet
Explanation:
Assuming point A is the center of the circle, arc DC has measure 180°. Arc DB has measure 40° less, so is 140°. Since you want this in terms of π, we need to convert the degree measure to radians. We do that by multiplying by (π/180) radians per degree:
arc DB = 140° = 140°(π/180°) radians
__
Now that we know the arc measure in radians, we can find the length of the arc. It is given by the formula ...
s = rθ
where r represents the radius and θ is the measure of the arc in radians.
The arc length is ...
s = (18 ft)(7π/9) = 14π ft
Arc DB has a length of 14π feet.