$\vec{A}$ and $\overline{\mathrm{B}}$ are two vectors and $\theta$ is the angle between them, if…

$\vec{A}$ and $\overline{\mathrm{B}}$ are two vectors and $\theta$ is the angle between them, if $|\overrightarrow{\mathrm{A}} \times \overline{\mathrm{B}}|=$ $\sqrt{3}(\overrightarrow{\mathrm{A}} \cdot \overline{\mathrm{B}})$, the value of $\theta$ is.
  1. $45^{\circ}$
  2. $30^{\circ}$
  3. $90^{\circ}$
  4. $60^{\circ}$

Solution

Finding the angle between the vectors: $\begin{aligned} & |A \times B|=\sqrt{3}(AB) \\ & |A||B| \sin (\theta)=\sqrt{3}|A||B| \cos (\theta) \end{aligned}$ Cancelling both sides we get $\begin{aligned} & \sin (\theta)=\sqrt{3} \cos (\theta) \\ & \frac{\sin (\theta)}{\cos (\theta)}=\sqrt{3} \\ & \tan (\theta)=\sqrt{3} \end{aligned}$ Hence $\theta=60^{\circ}$ Hence the angle between A and B is $60^{\circ}$

Asked in: NEET 2007

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