In my prior post, I introduced some basic Web Sketchpad geometry tools for constructing points, circles, segments, lines, and rays. These tools are great for getting started, but what happens when your needs grow more demanding? Suppose, for example, that you decide to build a tessellation pattern composed of equilateral triangles. Do you really want to build each triangle from scratch? Probably not.

With desktop Sketchpad, so-called “custom” tools can come to your rescue. By building an equilateral triangle just once, you can save it as a tool that can instantly create more equilateral triangles with just a few clicks of your mouse.

Despite their obvious value, custom tools lack visibility in Sketchpad’s interface. To find them, you need to burrow into Sketchpad’s custom tool menu, as shown below. Wouldn’t it be nice if using a square tool were as convenient as using the point, compass, and straightedge tools?

With Web Sketchpad, custom tools finally come out of the shadows. The web sketch below allows students to construct equilateral triangles, squares, rhombi, hexagons, and octagons simply by clicking the icons. If you click the equilateral triangle icon for example, you’ll see a preview of the triangle you’re about to create, with two of its vertices glowing. By dragging both vertices to locations of your choice, the triangle becomes permanent. If you then click the equilateral triangle icon again, you can create a second equilateral triangle. And if you drag the glowing vertices to coincide with two vertices from the first triangle, you can merge these points together, creating two attached triangles.

Use the above Web Sketchpad model to create tessellations. How many different ones can you make? If you make a mistake while building a tessellation, simply press the left arrow above the tool icons to undo one or more of the tools you’ve used.

If you’re interested in knowing how I built this set of polygon tools, I’ll describe briefly what I did: I began by constructing an equilateral triangle, square, rhombus, hexagon, and octagon in desktop Sketchpad. I took a screenshot of each polygon to be used as the icon for the tool. I then assembled the polygons into one Sketchpad document, followed a simple naming convention to indicate that these polygons were tools, and then fed the sketch through an exporter. Presto! The model was complete.

The opportunities for customizing sketches to contain only those tools relevant to an investigation are vast. In upcoming posts, I’ll present many more examples!