Let the vector v make an angle α with each of the three axes, then direction cosine of vare<cos‌α,cos‌α,cos‌α> Also, cos2α+cos2α+cos2α=1 Hence, direction cosine of v are <
1
√3
,
1
√3
,
1
√3
> or <−
1
√3
,−
1
√3
,−
1
√3
> So, the required line which makes equal angle with the coordinate axes is v=±
1
√3
i±
1
√3
j±
1
√3
k Now, the magnitude of the projection of the vector a=4i−3j+2j on line v. ∴ Projection of a along v=