Can anyone help me please to solve these two questions?

(3) Consider the system a: = siny, y = sins. (a) Find and classify the critical points of the system (b) Show that it is reversible (c) Show that there are therefore closed orbits around the xed point at (11', D) (Hint: write the system in terms of if: = :1: 7r and y and show that this new system is reversible). ((1) Show that the lines 3; = is are invariant, meaning any initial condition on the line has a trajectory on the line. (e) Sketch the phase portrait of the system. 1 (6) [bompare Strogatz, 6.8.7) Conaiderlthe DS r = (2301 y we, 3} = y(2: 1). (a) Plot the vector eld to help your intuition. (1)) Find the xed points (c) Plot the phase portrait (d) Argue using index theory why there can't be any closed orbits