4.1.1 For which real values of a does the equation 0 = sin(a0) give a well- defined vector field on the circle? For each of the following vector fields, find and classify all the fixed points, and sketch the phase portrait on the circle. 4.1.2 0 =1+2cos0 4.1.3 A = sin 20 4.1.4 0 = sino 4.1.5 0 = sin 0 + cos 0 4.1.6 0 =3+ cos 20 4.1.7 0 = sink0 where & is a positive integer