If vectors P, Q and R have magnitude 5, 12 and 13 units and overrightarrow P + overrightarrow Q = ov

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3-1.Vectors

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If vectors $P, Q$ and $R$ have magnitude $5, 12$ and $13 $ units and $\overrightarrow P + \overrightarrow Q = \overrightarrow R ,$ the angle between $Q$ and $R$ is

A

${\cos ^{ - 1}}\frac{5}{{12}}$

B

${\cos ^{ - 1}}\frac{5}{{13}}$

C

${\cos ^{ - 1}}\frac{{12}}{{13}}$

D

${\cos ^{ - 1}}\frac{7}{{13}}$

Solution

(c) $|\vec P|\; = \;5$, $|\vec Q|\; = 12$ and $|\vec R|\; = 13$

$\cos \theta = \frac{Q}{R} = \frac{{12}}{{13}}$

$\theta = {\cos ^{ – 1}}\left( {\frac{{12}}{{13}}} \right)$

Standard 11

Physics

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