hi, I have this problem i've been stuck with for a long time and i cant figure out what to do. if spherical coordinates are denoted (r,θ,ϕ) and cylindrical coordinates are denoted (ρ,ϕ,z), how do i express the radial unit vector in cylindrical coordinates, e(ρ), in terms of the spherical unit vectors (e(r), e(θ), e(ϕ)) corresponding to the same point? what i have tried is rewriting the spherical and cylindrical coordinates in terms of cartesians (x,y,z) and equating them, like this (the list goes cartesian, spherical, cylindrical): x = rsin(θ)cos(ϕ) = ρcos(ϕ) y = rsin(θ)sin(ϕ) = ρsin(θ) z = rcos(θ) = z which gives the result ρ = rsin(θ), from which i said e(ρ) = e(r)sin(θ). im not even sure this is right. then i hit a dead end. can anybody help me out, this is really getting on my nerves now. thanks.