With respect to a rectangular cartesian co

Your Ultimate Guide to JEE & NEET Question Solutions

With respect to a rectangular cartesian coordinate system, three vectors are expressed as
$\vec a = 4\hat i - \hat j$, $\vec b = - 3\hat i + 2\hat j$ and $\vec c = - \hat k$ 
where $\hat i,\,\hat j,\,\hat k$ are unit vectors, along the $X, Y $ and $Z-$axis respectively. The unit vectors $\hat r$ along the direction of sum of these vector is

A

$\hat r = \frac{1}{{\sqrt 3 }}(\hat i + \hat j - \hat k)$

B

$\hat r = \frac{1}{{\sqrt 2 }}(\hat i + \hat j - \hat k)$

C

$\hat r = \frac{1}{3}(\hat i - \hat j + \hat k)$

D

$\hat r = \frac{1}{{\sqrt 2 }}(\hat i + \hat j + \hat k)$
With respect to a rectangular cartesian coordinate system, three vectors are expressed as
$\vec a = 4\hat i - \hat j$, $\vec b = - 3\hat i + 2\hat j$ and $\vec c = - \hat k$ 
where $\hat i,\,\hat j,\,\hat k$ are unit vectors, along the $X, Y $ and $Z-$axis respectively. The unit vectors $\hat r$ along the direction of sum of these vector is
$\vec r = \vec a + \vec b + \vec c$
$ = 4\hat i - \hat j - 3\hat i + 2\hat j - \hat k$
$ = \hat i + \hat j - \hat k$
$\hat r = \frac{{\vec r}}{{|r|}} = \frac{{\hat i + \hat j - \hat k}}{{\sqrt {{1^2} + {1^2} + {{( - 1)}^2}} }} = \frac{{\hat i + \hat j - \hat k}}{{\sqrt 3 }}$