TI 89 Titanium Help - Plotting y^2 graphs.

[Shailen Sobhe]

The <Diamond> + F1 menu allows me to plot only Y= graphs.

How do I plot a graph of say, y^2=x+4 ?

You cannot plot y=Root(x+4) because you would miss the negative part of y.

If this is the only way to plot such graphs, how to you tell TI to plot a y= +/- Root(x+4) ?

Thanks.

 

[CompuChip]

You can plot Root(x + 4) and -Root(x + 4) simultaneously (e.g. using Y1 and Y2).
Or you can plot x^2 = y + 4 <=> y = x^2 - 4 and rotate your calculator

 

[Shailen Sobhe]

CompuChip, Thank you very much for this reply, but is it the only way I can plot graphs of y^2?

I surmise, like many would do as well, that rotating your calculator is awkward. Besides, though you could type the positive part for Y1, and then plot Y2=-Y1 as a shortcut, it is still cumbersome.

I am convinced that there should be a little TI 89 hack, or addon that would allow me to choose what left hand defining part of the equation that I wish to plot. For instance, rather than having only Ys in the <Diamond>F1 menu, I can choose between X and Y ( or Z for 3D).

In Microsoft Math 3.0, I am allowed to choose. So I just select X from the dropdown menu, and define X in terms of y^+4 and I get my graph.

Any ideas how this can be done in TI89 Titanium?

 

[CompuChip]

Hmm if typing -Y2 or rotating the screen or doing a sketch yourself on a piece of paper is too much work, maybe you can put your calculator in parametric mode and plot
X1(T) = T^2
Y1(T) = T
?

 

[Shailen Sobhe]

I guess plotting y-squareds in terms of x is a Texas Instruments limitation. Substituting for variables can be done, but then, imagine one has 5 or 6 graphs to plot and wishes to see where they intersect. Cumbersome.

Basically, I shall learn all the quadratic rules, graph transformations, and the graphs' general shapes.

Having such a graphical calculator is pointless, unless I code the little program in ASM that will allow me to choose my defining parameter (x or y ).

 

[George Jones]

Do what CompuChip says: using MODE set the Graph mode to PARAMETRIC. Then, press the green y=, and set yt1 = t and, since x = y^2 - 1, xt1 = t^2 - 1.