Question
The angle between two vectors $ - 2\hat i + 3\hat j + \hat k$ and $\hat i + 2\hat j - 4\hat k$ is ....... $^o$
✓
Answer
b
(b) $\cos \theta = \frac{{\vec A.\vec B}}{{|\vec A||\vec B|}} = \frac{{ - 2 + 6 - 4}}{{\sqrt {14} \sqrt {21} }} = 0$
(b) $\cos \theta = \frac{{\vec A.\vec B}}{{|\vec A||\vec B|}} = \frac{{ - 2 + 6 - 4}}{{\sqrt {14} \sqrt {21} }} = 0$
$\therefore \theta = 90^\circ $
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