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JEE Main201912 Apr 2019Evening ShiftMathematicsHeights and DistancesActual

The angle of the top of a vertical tower standing on a horizontal plane is observed to be 45 ° from a point A on the plane. Let B be the point 30 m vertically above the point A. If the angle of elevation of the top of the tower from B be 30 ° , then the distance (in m) of the foot of the tower from the point A is:

Options

  1. A15 3 + 3
  2. B15 1 + 3
  3. C15 5 - 3
  4. D15 3 - 3

Correct answer

A. 15 3 + 3

Step-by-step solution

t a n 45 o = 1 = x + 30 y ⇒ x + 30 = y ......(i) t a n 30 o = 1 3 = x y ⇒ x = y 3 ......(ii) from (i) and (ii) y = 15 3 + 3

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