trigonometry
posted by Michael on .
A lighthouse BC of unknown height stands on the edge of a cliff AB. From a point O, 2500 ft from the base of the cliff, an observer measures the angles of elevation of the top and bottom of the lighthouse and finds them to be 15°40' and 12°13'. How high is the lighthouse.

2500 (tan15°40'  tan12°13') feet
= 160 feet