18. From a boat on the lake, the angle of elevation to the top of a cliff is 1554'. If the base of the cliff is 967 feet from the boat, how high is the cliff (to the nearest foot)? (5 points) 19. Find the exact value of arccos (sin ( * )). For full credit, explain your reasoning. (5 points) 6 20. A person is watching a boat from the top of a lighthouse. The boat is approaching the lighthouse directly. When first noticed, the angle of depression to the boat is 1623'. When the boat stops, the angle of depression is 4929'. The lighthouse is 200 feet tall. How far did the boat travel from when it was first noticed until it stopped? Round your answer to the hundredths place. (5 points)