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3-1.Vectors
easy
જો $\vec P , \vec Q $ અને $\vec R $ ના મૂલ્યો $5$,$12$ અને $13$ એકમ છે અને જો $\vec P + \vec Q =\vec R $ હોય તો $\vec Q $ અને $\vec R $ વચ્ચેનો ખૂણો ........ હોય
A
${\cos ^{ - 1}}\frac{5}{{12}}$
B
${\cos ^{ - 1}}\frac{5}{{13}}$
C
${\cos ^{ - 1}}\frac{{12}}{{13}}$
D
${\cos ^{ - 1}}\frac{2}{{13}}$
Solution
$\begin{array}{l}
\,{\left( 5 \right)^2}\,\, + \;\,{\left( {12} \right)^2}\,\, = \,\,{\left( {13} \right)^2}\\
\Rightarrow \,\,\cos \theta \,\, = \,\,\frac{{12}}{{13}}\,\,\\ \therefore \,\,\theta \,\, = \,\,{\cos ^{ – 1}}\,\,\left( {\frac{{12}}{{13}}} \right)
\end{array}$
Standard 11
Physics
