NDA 2017 Maths · Mathematics · Three Dimensional Geometry · medium

A line equally inclined to the three coordinate axes has direction cosines ±(1)/(√3),±(1)/(√3),±(1)/(√3). 2. The distance of the point (1,2,3) from…

Single correct option

Consider the following statements:
1. A line equally inclined to the three coordinate axes has direction cosines

\pm\frac1{\sqrt3},\pm\frac1{\sqrt3},\pm\frac1{\sqrt3}

.
2. The distance of the point

(1,2,3)

from the

yz

-plane is

3

.
Which of the statements given above is/are correct?

Show answer and solution

Answer: (A) 1 only

1: equal angles give

l=m=n

and

l^2+m^2+n^2=1

, so each is

\pm\frac1{\sqrt3}

; true. 2: the distance from the

yz

-plane is the absolute value of the

x

-coordinate, which is

1

(the value

3

is the distance from the

xy

-plane); false. Only statement 1 is correct.

Original question written in the NDA 2017 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