A) \[{{60}^{\text{o}}}\]
B) \[{{120}^{o}}\]
C) \[{{70}^{o}}\]
D) \[{{180}^{o}}\]
Correct Answer: B
Solution :
\[{{R}^{2}}={{(3P)}^{2}}+{{(2P)}^{2}}+2\times 3P\times 2P\times \cos \theta \] ?(i) \[{{(2R)}^{2}}={{(6P)}^{2}}+{{(2P)}^{2}}+2\times 6P\times 2P\times \cos \theta \] ?(ii) by solving (i) and (ii), \[\cos \theta =-1/2\] Þ \[\theta =120{}^\circ \]
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