question_answer

If \[A=B+C\]have scalar magnitudes of 5, 4 3 units respectively, then the angle between A and C is

A) \[{{\cos }^{-1}}(3/5)\]

B)  \[{{\cos }^{-1}}(4/5)\]

C)  \[\pi /2\]

D)  \[{{\sin }^{-1}}(3/4)\]

Correct Answer: A

Solution :

 Here, triangle is \[\theta ={{\cos }^{-1}}\left( \frac{|C|}{|A|} \right)\] \[\theta ={{\cos }^{-1}}\left( \frac{3}{5} \right)\]