+ Reply to Thread
Results 1 to 7 of 7

Thread: Inequalities

  1. #1

    Inequalities

    Hi everyone,

    I can't graph inequalities.

    Can you help me?

    Thank in advance

    Emil

  2. #2
    Sketchpad Developer
    Join Date
    Oct 2010
    Location
    Philadelphia
    Posts
    71
    Hi Emil,

    There are two items in the Library that will help. Search the library for "inequality" to find them.

    dfishman has a sketch with one, two, or three inequalities plotted; the choice of inequality (greater than or equal vs. less than or equal) is determined by a test point. (In other words, put the test point where you want all inequalities to evaluate to true, and it will shade them appropriately.) dfishman provides both sample sketches and custom tools.

    The other is a set of inequality tools I posted a while ago: eight custom tools that accept a function as input and graph a particular inequality. There are tools for y>x, y≥x, y<x, y≤x, and also for x>y, x≥y, x<y, and x≤y. These tools require you to create the corresponding function, such as y = x^2, first, but it's best if you don't actually graph the function before using the tool. If you graph the function first the graph will appear as a solid line. If you let the custom tool graph the function, the graph will appear as either a solid or a dashed line depending on the inequality you've chosen.

    Happy sketching,
    Scott

    I hope you find these tools useful.

  3. #3
    Hi Stek,

    thank you for answer.

    I downloaded your sketch and that one by dfshman. Very interesting.
    But, I would like to know how graph an inequality from scratch.
    In Geogebra I introduce an inequality and the software graph it, with sketchpad I can't to do the same.
    When I try to introduce > or < symbols in the function window the keys are disabled.
    Would you like explain to me what kind of workaround I can use?

    Thanks

    Emil

  4. #4
    Sketchpad Developer
    Join Date
    Oct 2010
    Location
    Philadelphia
    Posts
    71

    Inequality Custom Tools

    Hi Emil, the workaround involves the custom tools that are in the documents you downloaded. Here's a step-by-step description of the method.

    1. Open the document Inequality Tools.gsp. (This makes the tools available.)
    2. Choose File | New Sketch.
    3. Choose Number | New Function, and define the function (for instance, f(x) = x^2).
    4. Press and hold the Custom Tools icon at the bottom of the toolbox. From the menu that appears, choose Inequality Tools | y>f(x).
    5. Click the function you created in step 3 above. The inequality is graphed and shaded.

    In the future you can skip step 1 by designating the folder containing Inequality Tools.gsp as your Tool Folder, by pressing and holding the Custom Tools icon and using the Choose Tool Folder command.

    Once you've done this, the inequality tools are always in the toolbox, and the workaround is really easy:
    1. Create the function corresponding the the desired inequality.
    2. Click the desired custom tool on it.

    For more information on using custom tools, and making use of your Tool Folder, see Help | Tools | Custom Tools | The Tool Folder.

    I hope this helps.

    --Scott

  5. #5
    Hi Scott and thank you very much.

    I didn't know the power of sketch. Wow!

    But if I introduce, for example, the function 2x+4 and I want to graph the inequality 2x+4> 3, how can I do it?
    Btw, when I introduce the function 2x+4 and then select y(x)>x the graph colorizes only a part of the interval. Why?

    I still need your help.

    Thanks

    Emil

  6. #6
    I still need help.

    Thanks

    Emil

  7. #7
    Sketchpad Developer
    Join Date
    Oct 2010
    Location
    Philadelphia
    Posts
    71
    Emil, I was swamped today. I think we're at the point that I need to see your sketch. Can you email it to me at this address: stek@kcptech.com

    Thanks,
    --Scott

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts