1) Rewrite the following expression in polar coordinates: (second derivative of z with respect to x) + (second derivative of z with respect to y) where x=rcos(theta) y = rsin(theta) i had first derivative of z with respect to x = (dz/dx)(dx/dr) + (dz/dx)(dx/d(theta)) same concept for y and then i just took the derivative of my dz/dz and dz/dy variables again 2) describe this surface in cylindrical coordinates z = rcos3(phi) express in cartesian coordinates i really do not get cartesian coordinates can anyone show me the generic method? 3) x = psin(phi)cos(theta) y = psin(phi)sin(theta) z = pcos(phi) near which points of R^3 can we solve for: p phi and theta in terms of x, y and z, describe the geometry behind your answer. again, i am really really weak in coordinate systems. any help is appreciated, thanks guys