Show this as indicated. Compare the amount of work.
(a) ey (sin h x dx + cos h x dy) = 0 as an exact ODE and by separation.
(b) (1 + 2x) cos y dx + dy/cos y = 0 by Theorem 2 and by separation.
(c) (x2 + y2) dx – 2xy dy = 0 by Theorem 1 or 2 and by separation with v = y/x.
(d) 3x2 y dx – 4x3 dy = 0 by Theorems 1 and 2 and by separation.
(e) Search the text and the problems for further ODE’s that can be solved by more than one of the methods discussed so far. Make a list these ODEs. Find further cases of your own.