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JAMB Mathematics 1991 Question 39

Question 39

Trigonometry

A flagstaff stands on the top of a vertical tower. A man standing 60m away from the tower observes that the angles of elevation of the top and bottom of the flagstaff are 64° and 62° respectively. Find the length of the flagstaff

  1. A.60(tan 62° − tan 64°)
  2. B.60(cot 64° − cot 62°)
  3. C.60(cot 62° − cot 64°)
  4. D.60(tan 64° − tan 62°)
Show the answer and explanation

Answer: D (60(tan 64° − tan 62°))

Explanation

The top of the flagstaff is 60 tan 64° high and its bottom (the top of the tower) is 60 tan 62° high. The flagstaff is the difference: 60(tan 64° − tan 62°).