PrepRung
Sign inSign up free

NDA 2021 Maths · Mathematics · Three Dimensional Geometry · easy

The direction cosines of the x-axis are (1,0,0). 2. The plane 3z=5 is parallel to the xy-plane.

Single correct option

Which of the statements is/are correct? 1. The direction cosines of the xx-axis are (1,0,0)(1,0,0). 2. The plane 3z=53z=5 is parallel to the xyxy-plane.
  1. A. 1 only
  2. B. 2 only
  3. C. Both 1 and 2
  4. D. Neither 1 nor 2
Show answer and solution

Answer: (C) Both 1 and 2

The xx-axis makes angles 0∘,90∘,90∘0^\circ,90^\circ,90^\circ with the axes, so its direction cosines are (1,0,0)(1,0,0). The plane 3z=53z=5, i.e. z=53z=\tfrac53, has normal along the zz-axis, as the xyxy-plane does, so the two planes are parallel. Both statements are correct.
Report a mistake

Original question written in the NDA 2021 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