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      Question

      The angle of elevation of the top of a building from the

      foot of a tower is 30Β° and the angle of elevation of the top of the tower from the foot of the building is 60Β°. If the height of the tower is 42 m, what is the height of the building?Β 
      A 42/√3 m Correct Answer Incorrect Answer
      B 14 m Correct Answer Incorrect Answer
      C 14√3 m Correct Answer Incorrect Answer
      D 42√3 m Correct Answer Incorrect Answer

      Solution

      Let AB and CD denote the tower and the building respectively. In β–³ABC, tan 60Β° = AB/BC β‡’ √3 = 42/BC β‡’ BC = 42/√3 m In β–³BCD, tan 30Β° = CD/BC β‡’ 1/√3 = CD/(42/√3) β‡’ CD = 14 m β‡’ h = 14 m

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