1. The problem statement, all variables and given/known data The force F (in pounds) acting at an angle θ with the horizontal that is needed to drag a crate weighing W pounds along a horizontal surface at a constant velocity is given by F= (μW)/(cosθ+μsinθ) Where μ is a constant called the coefficient of sliding friction between the crate and the surface. Suppose that the crate weighs 150 lbs and that μ=0.3 Find dF/dθ when θ=30°. Express the answer in units of pounds/degree. 2. Relevant equations F= (μW)/(cosθ+μsinθ) 3. The attempt at a solution F= 45/(cosθ+.3sinθ) dF/dθ=[(cosθ+.3sinθ)(d/dθ 45)]-[45(d/dθ cosθ + .3d/dθ sinθ)] / (cosθ+.3sinθ)2 dF/dθ=[-45(-sinθ+.3cosθ)]/(cosθ+.3sinθ)2 dF/dθ=(45sinθ-13.5cosθ)/(cosθ+.3sinθ)2 My problem is, when I plug in θ=30° isn't my answer in lbs not lbs/degree ?