Find the direction cosines of a vector $\vec{r}$ which is equally inclined with OX, OY and OZ are
Answer & explanation
Correct answer: option 1
Let $l, m, n$ be the direction cosines of $\vec{r}$. Since $\vec{r}$ is equally inclined with OX, OY and OZ.
Now, $ l^2 + m^2 + n^2 = 1 ⇒ 3l^2 = 1 ⇒ l = ±\frac{1}{\sqrt{3}}$
Hence, direction cosines of $\vec{r}$ are $±\frac{1}{\sqrt{3}}, ±\frac{1}{\sqrt{3}}, ±\frac{1}{\sqrt{3}}$