An incompressible Newtonian liquid is confined between two concentric circular cylinders of infinite length—a solid inner cylinder of radius R_i and a hollow, stationary outer cylinder of radius R_o (figure below, the z-axis is out of the page). The inner cylinder rotates at angular velocity ?. The flow is steady, laminar, and two-dimensional in the r?-plane. The flow is also rotationally symmetric, meaning that nothing is a function of coordinate ? (u_? and P are functions of radius r only). The flow is also circular, meaning that velocity component u_r = 0 everywhere. Generate an exact expression for velocity component u_? as a function of radius r and the other parameters in the problem. You may ignore gravity. The relationship between linear velocity and angular velocity is u = r?.