Plotting a specific point

[alcoonslists]

Trying to plot a specific point.  For example want to plot (3, pi/3) on the polar plane.  If I try POINTS & LINES/POINT, and then press "(", I can enter a first coordinate but cannot find a way to get to the 2nd coordinate.  Must be missing something simple.

Thanks,

Al

Al Coons

Department of Mathematics

Buckingham Browne & Nichols

Cambridge, MA

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

[Dennis Donovan]

Not sure if you are asking how to enter the y-coordinate after entering the x-coordinate (Cartesian coordinates), or how to enter a point in polar coordinates.

If trying to get to the y-coordinate, then it would seem like you should press Tab after entering the x-coordinate, but you need to press Enter, then the y-coordinate, then Enter to graph the point.

If trying to enter a point in polar, I don't know a way to do that except to type (r*cos(theta), r*sin(theta)).  Changing the graph type to Polar only changes how the graphs are entered, the coordinates of a point are still Cartesian coordinates.

Hope this helped.

Dennis Donovan

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From: alcoonslists <alcoon...@verizon.net>
To: tinspire tinspire <tins...@googlegroups.com>
Sent: Wednesday, May 23, 2012 8:41 AM
Subject: [tinspire] Plotting a specific point

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[alcoonslists]

Dennis,

Thanks for the the Enter key solution.  Helpful but I was hoping for polar plotting.

Wow.  I wonder why the points plot in rectangular coordinates if the graph type is polar?  Sure makes it hard to investigate the basic ideas of the polar plane.  Have to go to Sketchpad instead or am I missing something?

Al

[John Hanna]

Al,

    The ‘graph type’ is polar, the plane is Cartesian. Cool thing is that you can mix the different graph types on the same plane.

    It’s not hard to build a page that displays the polar coordinates of a point:

         Text for the formulas, then calculate.

         Combine (attach) the results along with parens and a comma to make it look like a coordinate pair.

 

Happy ‘programming’!

     John Hanna

     jeh...@optonline.net

     www.johnhanna.us

     T³ - Teachers Teaching with Technology

     "the future isn't what it used to be."

 

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[alcoonslists]

Hi John,

I agree that mixing the two types of graphs is really a nice feature.  Why not plot points in whatever mode the graphing is in?  You gain something and I am not sure what you loose???

I guess if I had choice between separate rectangular and polar plotting with full basic features such as appropriate concurrent tracing, point plotting, etc. versus being able to plot them both on the same plane, I prefer the former.

I don't agree that having to build pages and share documents is a good approach for investigating basic precalculus topics.

Al

[John Hanna]

 

… another issue is that the polar representation of a point is not unique.

 

The TI-Nspire was developed from the ground up with FILES as the driving force. You can’t do anything (except the measly ScratchPad) without first creating or opening a file. There’s nothing wrong with sharing them either. Almost all of T³ PD hinges on the study of premade documents and their place in the mathematics and science classrooms.

 

This took about 5 minutes to build. Graph the function, pot a point on, construct the segment, measure the segment and the angle and you’re done. Don’t want the Cartesian coordinates? Hide or delete them.