Parametric Graphing

[alcoonslists]

[John Losse]

It seems Al has found something that doesn't work the way it used to, perhaps because the new software version, for some reason, does not accept inequalities in a parametric function definition.

The attachment shows a workaround.  Basically, define the functions for x1(t) and y1(t) elsewhere, as functions of x, e.g. f1(x) = when(0 <= x <= s, sin(x) ), then go ahead and define x1(t) = f1(t).  Similarly define f2(x) = ..... and then y1(t)=f2(t).

John Losse

On Sunday, January 29, 2012 8:50:37 AM UTC-7, Al Coons wrote:

[alcoonslists]

On Jan 29, 2012, at 2:23 PM, John Losse wrote:

> It seems Al has found something that doesn't work the way it used to, perhaps because the new software version, for some reason, does not accept inequalities in a parametric function definition.
>
> The attachment shows a workaround. Basically, define the functions for x1(t) and y1(t) elsewhere, as functions of x, e.g. f1(x) = when(0 <= x <= s, sin(x) ), then go ahead and define x1(t) = f1(t). Similarly define f2(x) = ..... and then y1(t)=f2(t).
>
> John Losse
>

Thanks for the solution John. Creative. The problem is that the approach is such a kludge that while students and teachers can use it, it doesn't even feel very good as a black box tool. Entering the two parametric parts into F1 and F2 is just too confusing conceptually. I will pass this on to the other teachers and see what their reactions is.

As was discussed before, I hope TI will build these features into the OS. For those of us who teach parametric equations this is one of the few steps backwards for the TI-84.

Again John, thanks so much for taking the time to get us something that works. Timely and usable.

Al

[John Losse]

I agree, Al, it's not pretty or intuitive, and hopefully only temporary until the next software update, or maybe there is something we aren't seeing here.

> --
> To post to this group, send email to tins...@googlegroups.com
> To unsubscribe send email to tinspire+u...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com.au/group/tinspire?hl=en-GB?hl=en-GB
> The tns documents shared by group members are archived at
> https://sites.google.com/site/tinspiregroup/classroom-news/welcome-abouttime

[Marc Garneau]

Because the parametric still graphs with the slider & inequalities in John Hanna's document, that means it should still be possible to do. The problem/bug seems to be in the Entry Line for defining the relations.  Here's another workaround that stays in the realm of parametrics:

- Set up everything as before, except for defining x2(t) and y2(t), ie. define x1 and y1, set up your slider

- Plot something in x2, y2, without the inequalities.  This is just to get the x2,y2 plot to graph when it gets redefined.

- On a Calculator page or Notes page, define the parametric using the inequalities.

- Return to the Graphs page and it works!

Marc Garneau

<ParametricFakeOut -Losse.tns>--

[John Losse]

Yes, the problem seems to be in the how Nspire processes a parametric entry line.  Marc's method works, and avoids creating new functions.

[John Losse]

The problem also appears with polar graphing if you want to use an inequality in the r(theta) = box.  The same workarounds seem to work. I've also noticed that, though you can use Marc's workaround to define r(theta) with a when ... statement, you cannot use "expand entry line" to hide it or change its attributes. 

I imagine TI will fix this.  

[alcoonslists]

Wonderful.  Works and makes sense.  Thanks so much Marc.

Al

Al

-------------------------

Albert Coons

al_c...@bbns.org

Buckingham Browne & Nichols School

Gerry's Landing Road

Cambridge, MA 02138

(617) 800-2264

AP Statistics Web Site:  www.bbn-school.org/us/math/ap_stats

[alcoonslists]