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Geometry Expressions Newsletter 
January 2012 

From Java Applets to JavaScript/HTML5 apps

First there were Java Applets. In the 1990's at Saltire Software, we had an experimental geometry tool which created applets and inserted them in web pages. The results can be seen in our Geometry Applet Gallery. Two problems with Java applets are:  Users of the applet must have the Java runtime environment on their computer. This is not a problem for most computers, but smart phones and tablets typically do not have Java enabled.
 Creators of the applet must have a Java compiler.
These problems were sufficient to persuade us not to commercialize our Java Applet generation technology. The advent of JavaScript removed both of these obstacles.  JavaScript/HTML5 apps run inside the browser without any additional plugins. They work well on computers, tablets and smart phones.
 JavaScript source code is embedded directly in the web page, and no compilation is necessary.
All this means that you can generate a web page with a JavaScript app at the press of a button from within Geometry Expressions. We recreated our Geometry Applet Gallery so you can compare the Java Applet Version with the JavaScript Version.


How to...create an applet with draggable points
 We illustrate how to create an app with points which the user can drag. Our app will display a triangle along with the lengths of its sides and its area. The user will be able to drag the vertices of the triangle.
 First draw a triangle.
 Constrain the coordinates of the vertices of the triangle, leaving the default variable names in place. (To be draggable, a point must have both coordinates constrained to be variables.)
 Now Calculate Symbolic measurements for the lengths of its sides and for its area. (Only symbolic measurements can appear in the app).
 Do File / Export / HTML5/JavaScript App
 Fill in the app dialog, being sure to set Autoscale to False.
The finished web page may be seen here.

Problem of the Month  Given a triangle ABC, points D,E,F are defined to be proportion t along the sides AB, BC, CA respectively. Point G is at the intersection of AE and BF. Point H is at the intersection of BF and CD. Point I is at the intersection of CD and AE. Using Geometry Expressions (or otherwise) show that the loci of G,H and I as t varies are portions of ellipses. Show further that they are portions of the same (translated) ellipse. An app illustrating this property is here. Under what circumstances is the ellipse a circle? 



Electronic Book Bundle
 10 Geometry Expressions eBooks are now available as a bundle for the recessionfriendly price of $79.95 Bundle includes:
 The Tortoise and Achilles
 Calculus Explorations
 The Farmer and the Mathematician
 Developing Geometry Proofs
 101 Symbolic Geometry Examples
 101 Conic Sections Examples
 Using Symbolic Geometry to Teach Secondary School Mathematics
 Connecting Algebra and Geometry through Technology
 Function Transformations
 Exploring with Geometry Expressions
Learning Calculus with Geometry Expressions is a unique electronic resource containing lectureready slides and labready Geometry Expressions files. Available for $6.99 per chapter, or $34.95 for the whole book.


Videos

See our YouTube channel for videos exploring the new features in Geometry Expressions.





