Show that the scalar product of two vectors obeys the law of commutative.

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If $\theta$ is the angle between $\vec{A}$ and $\vec{B}$, then scalar product

$\overrightarrow{\mathrm{A}} \cdot \overrightarrow{\mathrm{B}} =\mathrm{AB} \cos \theta$

$=\mathrm{BA} \cos \theta$

$\therefore \quad \overrightarrow{\mathrm{A}} \cdot \overrightarrow{\mathrm{B}}$ $=\overrightarrow{\mathrm{B}} \cdot \overrightarrow{\mathrm{A}}$

$[\because \mathrm{AB}=\mathrm{BA}]$

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  • [NEET 2017]

Find the angle between two vectors with the help of scalar product.