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Home  >>  JEEMAIN and NEET  >>  Mathematics  >>  Class12  >>  Vector Algebra

For any vector $\overrightarrow a\:\:and\:\:\overrightarrow b$ the angle between $|\overrightarrow a|\overrightarrow b+|\overrightarrow b|\overrightarrow a$ and $|\overrightarrow a|\overrightarrow b-|\overrightarrow b|\overrightarrow a$ is ?

$\begin{array}{1 1} 0 \\ \large\frac{\pi}{4} \\ \large\frac{\pi}{3} \\ \large\frac{\pi}{2} \end{array} $

1 Answer

Angle $\theta$ between $|\overrightarrow a|\overrightarrow b+|\overrightarrow b|\overrightarrow a$ and $|\overrightarrow a|\overrightarrow b-|\overrightarrow b|\overrightarrow a$ is
$cos\theta =\large\frac{(|\overrightarrow a|\overrightarrow b+|\overrightarrow b|\overrightarrow a).(|\overrightarrow a|\overrightarrow b-|\overrightarrow b|\overrightarrow a)}{|(|\overrightarrow a|\overrightarrow b+|\overrightarrow b|\overrightarrow a)|\:||\overrightarrow a|\overrightarrow b-|\overrightarrow b|\overrightarrow a|)}$
$=0$
$\therefore\:\theta=\large\frac{\pi}{2}$
answered Nov 29, 2013 by rvidyagovindarajan_1
 

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