Question:
A vector $\vec{r}$ is inclined at equal angles to the three axes. If the magnitude of $\vec{r}$ is $2 \sqrt{3}$ units, find $\vec{r}$
Solution:
As the vector 
makes equal angles with the axes, their direction cosines should also be same
So, l = m = n
And we know that,
l2 + m2 + n2 = 1 ⇒ l2 + l2 + l2 = 1
3l2 = 1
l = ± 1/√3
