Question
Find the angle between two vectors $\vec A = 2\hat i + \hat j - \hat k$ and $\vec B = \hat i - \hat k$ ....... $^o$
✓
Answer
b
$\cos \,\theta = \frac{{\vec A.\vec B}}{{AB}} = \frac{{2 + 1}}{{\sqrt 6 + \sqrt 2 }} = \frac{3}{{\sqrt 6 \sqrt 2 }} = \frac{{\sqrt 3 }}{2}$
$\cos \,\theta = \frac{{\vec A.\vec B}}{{AB}} = \frac{{2 + 1}}{{\sqrt 6 + \sqrt 2 }} = \frac{3}{{\sqrt 6 \sqrt 2 }} = \frac{{\sqrt 3 }}{2}$
$\therefore$ $\theta = 30^o$
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