Here Comes Construction!

For over a year, my colleague Scott and I have enjoyed giving you peeks into the impressive development work being done by the Web Sketchpad team at KCP Technologies and McGraw Hill.  Every time I take a desktop Sketchpad model and convert it to Web Sketchpad with a press of a button, I’m impressed by how effortlessly and well the Web Sketchpad technology replicates the desktop experience of using Sketchpad.

But there is one element of desktop Sketchpad that has been conspicuously missing from Web Sketchpad; a fundamental ability of Dynamic Geometry software that’s essential to the mathematical and pedagogical value of Sketchpad. That element is construction.

It’s fashionable these days to think that students can learn mathematics simply by playing games in which they interact with objects already on the screen. I can think of few iPad apps  in which students build their own mathematics from scratch. Indeed, our own Sketchpad Explorer app for the iPad is guilty of not allowing students to construct objects—and we’ve heard plenty of requests for adding that functionality!

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When students open a new Sketchpad file on their computer, they’re presented with a blank screen. Much like the experience of starting with a blank word-processing screen, it’s up to students to decide what to create. There to help them are a variety of tools found in the toolbox (shown at right). These tools include a point tool, a compass tool, a straightedge tool, and a polygon tool.

Below is a Web Sketchpad model that displays a blank screen with a point, compass, segment, line, and ray tool ready for you to use. For those of you familiar with desktop Sketchpad, you’ll notice that these tools don’t follow the same conventions as their desktop counterparts. Notice, for example, that when you click or tap on the segment tool, you immediately see a preview of the segment in the sketch. The endpoints of the segment glow, indicating that you can drag these points wherever you like to place the segment. Try constructing a triangle, a circle and its radius, and an isosceles triangle. You’ll see that when you drag the glowing points, you can merge them with other points or attach them to other objects, like circles and lines. If you’d like to undo one ore more of the tools you’ve used, simply press the left arrow above the tool icons.

A caveat: We’re still in the early phases of developing tool functionality for Web Sketchpad, so features like the ability to hide objects, change colors, and add labels are not yet implemented.

You also might wonder about other functionality in desktop Sketchpad, like the ability to construct perpendicular lines, transform objects, and use “custom” tools that construct objects like squares nearly instantly with just a few clicks of your mouse. These capabilities do exist in Web Sketchpad. You’ll be reading about them (and experimenting with them) in the weeks to come here on our blog!

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