1. The problem statement, all variables and given/known data A lady pushes a box with mass (m) with force (F) at a horizontal angle of θ. There is a static friction (μ) 2. Relevant equations ƩFy = Fn - m*g - F*sinθ = 0 ƩFx = F*cosθ - μFn = 0, where μFn is the force of friction. 3. The attempt at a solution F*cosθ - μ*Fn = 0 μ*Fn = F*cosθ; and Fn = m*g + F*sinθ So, μ(m*g + F*sinθ) = F*cosθ μ = (F*cosθ)/(m*g + F*sinθ) But the textbook's answer is μ = 1/tanθ. Is it wrong? I almost get their answer except for the m*g. And when I use dummy values I don't get the same answer as the book, so I am pretty sure that my problem is from not simplifying the equation enough.