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From the top of a 45 ft. fire tower, a forest ranger sees his partner on the ground
at an angle of depression of 40 degrees.
How far is the partner from the forest ranger above the tower?
A.53.63 ft. B.58.74 ft.
C.70.01 ft. D.72.38 ft.
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You have a right-angled triangle with vertical leg of 45 ft (the tower),
and the acute angle adjacent to this leg of 90° - 40° = 50°.
Recall the definition of the cosine of an acute angle in right-angle triangle
and write this equation connecting the leg, the hypotenuse length and the concluded angle
cos(50°) = ,
where x is the distance under the problem's question.
From this equation, find x = = = 70.01 ft. ANSWER
Solved.