Graphing Non-f(x) Functions on TI-89 Calculator

[jaredmt]

i was wondering if i could graph something like:
2x + 3y = 7
or
3y^2 + 2x^2 -3x +6 = 0

where the function doesn't always start with plain f(x). is it possible to do this on ti 89?

 

[qntty]

If y=f(x), then solve for y. If you're asking about things that don't have nice explicit forms, eg a 3rd degree polynomial in y, then yes, the TI-89 can solve those for you.

 

[Nabeshin]

Fairly sure you can only graph explicit functions on the TI-89, so like qntty says, you'll have to solve for y (but the TI-89 will do this for you).

 

[HallsofIvy]

Sometimes, but not always, you can write implicitely defined functions in terms of explicit functions of a parameter. For example, you can graph x²+ y²= 1, a circle, in parametric graphing mode with x= cos(t), y= sin(t).

 

[jambaugh]

Now the TI-89 is programmable so you might search the TI site for packages you can upload to expand its capacities or write your own. At worst you can graph the inequality f(x,y) < 0 by iterating over the coordinates on the visible screen and plotting the ones satisfying the inequality. The boundary will then be your curve.

 

[qntty]

Yes, if you want to graph an implicit equation without having to first solve for a variable, you could easily write a program to solve it and input it into Y1.