(c) The coordinates (r, 0, 2), where r and 8 are the polar coordinates in the ry plane, and z is the usual Cartesian coordinate, are called the cylindrical coordinates. In these coordinates, the Laplacian takes the form A a2 1 a 1 22 a2 + + + ar2 rar p2 a82a22 Let 12:= {(1, y, z) € R3 : x2 + y² <1, 0