Monday, July 28, 2014

#July2014Challenge: Dynamic Polar Curve Plotter

In my last post I talked about how to plot polar curves in Geogebra.  As I neared the end of the post I remembered how the use of sliders can enhance this topic.  

Below is a polar graph plotter.  You can try this out now by dragging the slider alpha from 0 to 360 degrees.  Move the slider back to 0 degrees and type in another function such as 3cos(5x), or 12/(2-sin(x)).  A copy of this tool is available from the Geogebratube site here.  

I always have so much fun playing around with Geogebra, but I know it can be time consuming.  In case you have the extra time and are interested, I am also including directions on how to plot the polar curves and add the slider. Some of this is a repeat from my blogpost on how to plot polar curves with Geogebra.  

Let's say I want to plot the polar curve below.

Start by typing the following function into the input bar at the bottom of a Geogebra page:

Hit enter, then hide this function.  Next we will add a slider called alpha that goes from 0 to 360 degrees.  From the toolbar select the button that says a=2.  If you can't find this button, open the dropdown menu from the button that is second from the right (see below).

VERY IMPORTANT!!!  To add the slider to your graphics view, click on the location where you want the slider to be.  I usually pick the top right of the graphics view.  It is a pain to move these sliders once you place them on the screen, so better to get it right the first time.

The default for a slider value is a number from -5 to 5.  We want an angle, so select the angle button on the left, as shown below.  The default values shown below will work for our polar curve plotter, so you can press apply to set up your slider.

After this we are going to use the following command:

Below is what I will enter into the various command parts:

If you read the blogpost from yesterday, you will notice that my end value was 360 degrees.  To make this a dynamic plotter, I changed my end value to match the value of the slider alpha.  Once this is finished, you will be able to plot the parabola below by dragging the slider value from 0 to 360 degrees.  

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