we have a non magnetic but anisotropic dielectric medium which has the following relationships between D and E Dx = k1*Ex, Dy = k2*Ey, Dz = k3*Ez we have to show that waves propogate in the z-dir'n at one speed only. I can't get the wave eq'n to fall out. Usually you just use Maxwell's equations and the vector identity curl(curl(E)) = grad(divE)- grad squared E and set divE = 0. You can usually say this because in a dielectric there is no free charge therefore divD = 0 and in an LIH medium E is proportional to D therefore divE = 0 . Instead now I have to include the grad(divE) expression and the algebra doesn't even resemble the wave eq'n. I'd appreciate any hints on where I've gone wrong.