A vertical tower standing at the corner of a rectangular field subtends angles of 60^\circ and 45^\circ at the two nearer corners. If \theta is the angle that the tower subtends at the farthest corner, then what is \cot \theta equal to?

  1. A. \frac{1}{2}
  2. B. 2
  3. C. \frac{2}{\sqrt{3}}
  4. D. \frac{4}{\sqrt{3}}

Correct Answer: C. \frac{2}{\sqrt{3}}

Explanation

Let the tower height be h. The distances to the nearer corners (forming the rectangle's sides) are h \cot 60^\circ = h/\sqrt{3} and h \cot 45^\circ = h. The distance d to the farthest corner is the diagonal: d = \sqrt{(h/\sqrt{3})^2 + h^2} = h\sqrt{4/3}. Thus, \cot \theta = \frac{d}{h} = \frac{2}{\sqrt{3}}.

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