Note how the red unit radial arrow (u_r) and the unit vector u_theta perpendicular to it, changes as the red u_x slider is moved with the mouse. Motion is simulated counter clockwise by decreasing the value of u_x.
Similar changes in the blue slider (u_1) effects the blue arrow referring to u_t (tangential to motion) and the unit blue vector u_n points into the circle.
Note that if u_x=u_1 then the blue and red unit vectors are NOT the same.
You can enlarge the circle using the slider for the parameter a.
