# Calculators How do I graph (In TI-89 titanium) where Y is the independent Variable?

1. Sep 9, 2007

### Migkiller

Right now I'm doing Centroids in my math class. we are given two functions.
X=-y
and
X=2y-y^2.

My question is, how do I graph these two functions on my TI-89 titanium. The Y=editor is displayed as y(x). Is there a way to change it to X(y). I was able to plot it out on paper, but I use my calculator to check my work. Any help is appreciated thanks.

2. Sep 9, 2007

### G01

Off the top of my head, I can't think of any way, but I don't do much graphing with mine. The easiest solution I can think of is (This may be stupid of me to point out, since it's kind of obvious) to replace y with x in the calculator and vice-versa and just keep track of the change of notation in your head?

If there is a way to do what you ask, I'm sure someone here know how to, but I thought I'd point out the "quick and dirty" fix for the problem.

3. Sep 9, 2007

### Hurkyl

Staff Emeritus
A rotation works too: (x, y) --> (y, -x). That way, you can undo the rotation 'by hand'.

4. Sep 10, 2007

### JonF

rotate your calculator by pi/2 :)

5. Sep 10, 2007

### George Jones

Staff Emeritus
Use PARAMETRIC mode, setting, for example, y = t and x = 2t - t^2.

6. Sep 10, 2007

### Migkiller

7. Sep 10, 2007

### Migkiller

8. Sep 10, 2007

### George Jones

Staff Emeritus
I can't tell problem you're having. In PARAMETRIC mode, I get the exact graph. I set tstep = 0.05.

9. Sep 10, 2007

### jersiq1

You should just be able to use the SOLVE function in the catalog from the main screen.
I can't remeber what menu it is under, it may be ALGEBRA.
SOLVE(X=2y-y^2,y) {ENTER}
The copy the answer into the Y editor. If there are roots, you have to manually enter each root i.e if you want to look at the sq_rt of x you have to input two seperate equations

y=sq_rt(x)
and
y= -sq_rt(x)