1. The problem statement, all variables and given/known data A reasonable approximation for the two-dimensional incompressible laminar boundary layer on the flat surface in Fig. P4.17 is u ≈ U(2*(y/δ) - 6*(y3/δ4) + y4/δ4) δ = Cx1/2 where C is a constant y ≤ δ 2. Relevant equations 3. The attempt at a solution Incompressible so density is constant, 2D flow so no z component, continuity equation reduces to ∂u/∂x + ∂v/∂y = 0 For the x component, I got [ (-2y/δ2) + (6*y3/δ4) - (4*y4/δ5) ] But there is supposed to be a dδ/dx term attached to each term. Where does this term come from? Is it some kind of chain rule thing? Thanks!