diff(w(r, theta), r)/r + diff(w(r, theta), r, r) + diff(w(r, theta), theta, theta)/r^2 = r^3*cos(3*theta)
diff(w(r, theta), r)/r + diff(w(r, theta), r, r) + diff(w(r, theta), theta, theta)/r^2 = r^3*cos(3*theta)
Can it be solved without boundary conditions?