NDA 2017 Maths · Mathematics · Three Dimensional Geometry · easy

The cosine of the angle which the line (x-1)/(2)=(y+2)/(3)=(z-3)/(6) makes with the z-axis is

Single correct option

The cosine of the angle which the line

\frac{x-1}{2}=\frac{y+2}{3}=\frac{z-3}{6}

makes with the

z

-axis is

Show answer and solution

Answer: (A) $\frac67$

Direction ratios

(2,3,6)

have magnitude

\sqrt{4+9+36}=7

, so the direction cosines are

\frac27,\frac37,\frac67

. The

z

-axis cosine is the third one,

\frac67

. The others are the cosines with the

x

- and

y

-axes.

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