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3-1.Vectors
medium
The angle between two vectors $ - 2\hat i + 3\hat j + \hat k$ and $\hat i + 2\hat j - 4\hat k$ is ....... $^o$
A
$0$
B
$90$
C
$180$
D
None of the above
Solution
(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 $
Standard 11
Physics