1. The problem statement, all variables and given/known data "The flow of a fluid past a wedge is described by the potential ψ(r,θ) = -crαsin(αθ), where c and α are constants, and (r,θ) are the cylindrical coordinates of a point in the fluid (the potential is independent of z). Verify that this function satisfies Laplace's equation, Δψ = 0." 2. Relevant equations Δ is the Laplacian operator 3. The attempt at a solution I have proved the statement, but I feel like I had to fudge the Chain Rule in order for it to work out. I have that δ/δr(ψ) = -αcrαsinαθ but I think that since α is some constant I ought to have δ/δr(ψ) = -αcr(α-1)sinαθ, and the second partial derivative would yield -α(α-1)cr(α-2)sinαθ. If done this way, the terms will not cancel and I cannot conclude the Laplacian is equal to zero. Why doesn't the power of α change if it's a constant? I thought that d/dx(xn) = nx(n-1), so why does that not seem to apply in this case? Thanks for any insight.