InterviewSolution
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InterviewSolution
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If `vec(A) = 3 hat(i) + 6 hat(j) - 2hat(k)` , the directions of cosines of the vector `vec(A)` areA. `(3)/(7) ,(6)/(7) ,(2)/(7)`B. `(3)/(7) ,(6)/(7) , (-2)/(7)`C. `(6)/(7) ,(2)/(7) ,(3)/(7)`D. `(2)/(7) ,(3)/(7) ,(6)/(7)` |
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Answer» Correct Answer - B If `vec (r ) = x hat(i) + y hat(j) + z hat(k) , r = sqrt(x^(2) + y^(2) + z^(2))` `alpha , beta , gamma` : angles made by `vec(r )` with coordinates axes `cos alpha = (x)/( r) , cos beta = (y) /( r ) , cos gamma = (z)/( r )` Direction cosines ,` cos alpha , cos beta , cos gamma` `vec(A) = 3 i + 6 j - 2k , |vec(A)|= A = sqrt((3)^(2) + (6)^(2) + (-2)^(2)) = 7` `cos alpha = (3)/(7) , cos beta = (6)/(7) , cos gamma = (-2)/(7)` |
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