What are the direction cosines of {arrow}{r} ?

Correct Answer is : [12,32,0]≤ft[ 1/2, {{3}}{2}, 0 ][21,23,0]

Correct Answer is : [12,32,0]≤ft[ 1/2, {{3}}{2}, 0 ][21,23,0]

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UPSC NDA Math Model Paper 4

Question : 107 of 120

Marks: +1, -0

\overset{\rightarrow}{r} ?

Solution:

It is given that the vector makes an angle of

60^{\circ}

with

x

-axis, angle of

30^{\circ}

We already established that the vector makes

90^{\circ}

angle with

z

-axis.

Therefore, direction cosines are given by:

\left[ \cos 60^{\circ}, \cos 30^{\circ}, \cos 90^{\circ} \right]=\left[ \frac{1}{2}, \frac{\sqrt{3}}{2}, 0 \right]

Thus, the direction cosines are

\left[ \frac{1}{2}, \frac{\sqrt{3}}{2}, 0 \right]

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