These instructions will allow you to create customized graph theory problems within the directory MyExercises provided in the zipped file PlanarGraphs.zip. Download this file and unzip it in a location where you can easily find the files and folders. Here you will find all of the files on this website along with the MyExercises folder and the Flash MX source code for these tools. You can follow the instructions here or open the identical planarInstructions.html from the unzipped file.
Click here to open the instructor's "GraphMaker" tool in its own window. Print these instructionsor resize things to be able to see these instructions and the GraphMaker tool at the same time.
Open the file "planar.txt" within the MyExercises directory. Note that the only thing in the file is the string problems=. This is where we will place the data that specifies our graphs. Leave this file open and return to the GraphMaker tool.
Follow the instructions in GraphMaker to draw a graph that you want your students to test for planarity. Here is a quick reference for the functions available in case it is not clear.
- When RemoveNodes, DrawNodes, or EditLines buttons are pressed, you activate/deactivate a mode with specific editing abilities. You will be able to tell that mode is active by the gray box that appears behind the relevant button.
- When DrawNodes is active, clicking on the screen will produce a node. Once the maximum allowable number of nodes is reached, you will be "cut off" from this function.
- When RemoveNodes is active, clicking on a node will delete it along with any incident edges.
- When EditLines is active, clicking on a pair of nodes will either draw an edge between them or remove the edge between them if an edge is already there.
- When none of this buttons is active, you can freely drag nodes to rearrange your graph.
- The Clear button erases your graph so you can start over.
- The Finished button leaves the editor and shows you the data that defines your graph.
The data for your graph is shown in a text box in the middle of the screen. Use your mouse (or click in the box and press Ctrl+A to "Select All") to select all text that is there, and press "Ctrl+C" to copy it. Go to the still-open file planar.txt, and paste (Ctrl+V) this line of data to the end of what is already there. (This is just the string "problems=" initially.)
Test your exercises by opening the file planarGraphs.html in your browser. You will notice that the problems are given in random order. Note that you can include more instructions or information before and/or after the actual Flash applet, if desired.
If you do not want to use the name "planar.txt" for your data file, you can change this in the first line of the script in frame 1 of the planarGaphs.fla source file. Also, if you want to have the problems not randomized, you can change the second line of the script in frame 1 to set the variable randomQuestions to false. Note that you must have the Flash MX authoring system to make these changes.
Direct questions or comments to Doug Ensley (deensl@ship.edu), Professor of Mathematics, Shippensburg Univerisity