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A tower stands vertically on the ground. From a point on the ground, which is 17 m away from foot of the tower, the angle of elevation of the top of the tower is found to be 30°. What is the height of the tower ?

  • A.\(17/\sqrt{3}\)
  • B.\(17\sqrt{3}\)
  • C.17
  • D.\(3\sqrt{17}\)

Answer: A

The height of the tower is \(17/\sqrt{3}\) m.

The tower, the ground and the line of sight form a right triangle with the 30° angle at the observer, the 17 m distance as the adjacent side and the height h as the opposite side.

\[ \begin{aligned} \tan 30^{\circ} &= \frac{h}{17} \\ h &= \frac{17}{\sqrt{3}} \approx 9.8\ \text{m} \end{aligned} \]

\(17\sqrt{3}\) would be the height for a 60° angle of elevation, and 17 m would need a 45° angle.

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