The TI-89 has many features that are particularly useful to ode and to
calculus in general. These are taken directly from the ti89 manual which
is a downloadable pdf file as well as the physical book which came with
the calculator:

ode features:
	Chapter 11 of the manual
	1. First order systems of ode's. 
		a. numerical methods for approximate solutions (Euler and RK)
		b. deSolve function for exact solutions 
	2. Non-trivial graphing choices:
		a. Single ode of 1st order. SLPFIELD or FLDOFF (DIRFLD causes an error)
		Can plot multiple integral curves on the same plot.
		b. Single ode of 2nd order, convert to a system of two 1st order
		odes. (Hint: y1(t) is the function and y2(t) is y1'(t), so
			y'' + y' + y = 0 becomes (let y2 be y' and y1 be y)
			y1'(t) = y2(t) and y2'(t) = - y2(t) - y1(t).
		Use DIRFLD for 2nd order ode or systems of 2 1st order ode's
		c. 3rd and higher require FLDOFF (field off)
		d. Initial conditons can be a set of values, or alternately
		use the ncurves variable in the window menu. You can also do
		it interactively.

discrete system features:
	Chapter 9 of the manual.
	1. graphing recursively defined sequences like u_n = n u_{n-1} u_1 = 1
	2. TIME plots: n on x axis, u(n) on y axis
	3. WEB plots: (u_{n-1}, u_n)
	4. CUSTOM plots: you select the x and y axis

	You don't have to plot all of sequence, you can start/stop plotting
	earlier or plot just the even n.

	You can plot Line Dot Square or Thick.

	Systems of sequences (Custom for predator/prey -- rabbits eating banana)

	generating tables from sequences.