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NDA 2019 Maths · Mathematics · Three Dimensional Geometry · medium

The distance of the point (2,-3,5) from the y-axis is

Single correct option

The distance of the point (2,−3,5)(2,-3,5) from the y-axis is
  1. A. 29\sqrt{29}
  2. B. 33
  3. C. 38\sqrt{38}
  4. D. 13\sqrt{13}
Show answer and solution

Answer: (A) 29\sqrt{29}

The foot of the perpendicular from (2,−3,5)(2,-3,5) to the y-axis is (0,−3,0)(0,-3,0), so the distance is 22+52=29\sqrt{2^2+5^2}=\sqrt{29}. The value 33 is the distance from the xz-plane, a common confusion between distance from a plane and from an axis; 38\sqrt{38} is the distance from the origin.
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Original question written in the NDA 2019 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake