Is there another way in maple to code `union`. I am not confident using this function and was wondering if there was a perhaps longer/different way to do the same thing?

Thanks!

I am trying to do taylor series expansion around the critical point, but I keep getting an error, because I think Maple is taking my critical point as function {x(t) = 5, y(t) = 10}. I would like to get just the output of x(t)=  from the list of critical points. Ex. Does anyone know the maple code to get "5" and "10" from the list of critical points without typing in 5 and 10.

3.mw Here is my maple code that shows the animation for different values in b. The equation this is referring to is given in the code. I have done (b) and (c), and the animation is in the code, but I am not sure where for what value of b for the behavior changes, any tips on what to look for would be really helpful.

However, I am primarily concerned with (d) as I am not sure how to demonstrate periodic behaviour with dsolve. Thanks for the help!   

How to use a Lyapunov function to prove the stability of a system of differential equations and then check the stability? My initial thoughts were to use a contour plot?