If vectors \( P, Q \) and \( R \) have magnitude 5,12 and 13 units and \( \vec{P}+\vec{Q}=\vec{R....

Question If vectors \( P, Q \) and \( R \) have magnitude 5,12 and 13 units and \( \vec{P}+\vec{Q}=\vec{R} \), the angle between \( Q \) and \( R \) is
(A) \( \cos ^{-1} \frac{5}{12} \)
(B) \( \cos ^{-1} \frac{5}{13} \)
(C) \( \cos ^{-1} \frac{12}{13} \)