7.The total force needed to drag a box at constant speed across a surface with coefficient of kinetic friction μ is least when the force is applied at an angle θ such that
(A) sinθ = μ
(B) cosθ=μ
(C) tan θ=μ
(D) cotθ=μ
(E) secθ =μ
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統計: A(0), B(1), C(8), D(1), E(1) #3224653
統計: A(0), B(1), C(8), D(1), E(1) #3224653