Let r, , Ф be spherical coordinates. If u(r, , Ф) satisfies 2u = 0, show that

Let r, θ, Ф be spherical coordinates. If u(r, θ, Ф) satisfies ∆2u = 0, show that v(r, θ, Ф) = u(1/r, θ, Ф/r satisfies ∆2u = 0. What does this give for (16)?