(1 point) To model diffusion in a thin ring, we replace the usual spatial coordinate by the angle 8, noting that the unknown function u= u(0,1) must be 21- periodic in @ for all time. (PDE) u; = 2ug0 - 1134 sin(90) 300 sin(50), -0, (BC) u(@+ 27, t) = u(0,1), - 0, (IC) u(0,0) = 8 + 4 cos(20) - 7 sin(90), -00 0, (BC) u(@+ 27, t) = u(0,1), - 0, (IC) u(0,0) = 8 + 4 cos(20) - 7 sin(90), -00