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If `vecA = vecB + vecC` and the magnitudes of `vecA, vecB and vecC` are 5,4 and 3 units respecetively, the angle between `vecA` and `vecC` is :A. `cos ^(-1)(3//5)`B. `cos ^(-1)(4//5)`C. `pi//2`D. `sin^(-1)(3//4)` |
Answer» Correct Answer - A `vecC + vecB = vecA` `rArr " "vecB = vecA - vecC` `" "|vecB|=|vecA - vecC|` `" "4=sqrt(5^(2) + 3^(2) - 30 cos theta)` `" "16-34 =-30cos theta` `" "(-18)/(-30) =cos theta" "rArr" "cos theta= (3)/(5)` `" " theta = cos ^(-1).(3)/(5)` |
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