The angle between the vectors i - j + k and i + 2j + k is - Vidyadip

MCQ

The angle between the vectors $i - j + k$ and $i + 2j + k$ is

A
${\cos ^{ - 1}}\left( {\frac{1}{{\sqrt {15} }}} \right)$
B
${\cos ^{ - 1}}\left( {\frac{4}{{\sqrt {15} }}} \right)$
C
${\cos ^{ - 1}}\left( {\frac{4}{{15}}} \right)$
✓
$\frac{\pi }{2}$

✓

Answer

Correct option: D.

$\frac{\pi }{2}$

d
(d) $(i - j + k)\,.\,(i + 2j + k) = \sqrt 3 \sqrt 6 \cos \theta $

$ \Rightarrow \cos \theta = \frac{0}{{\sqrt 3 \sqrt 6 }} \Rightarrow \theta = \frac{\pi }{2}.$

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