Geometry Expressions

Geometry Expressions Webinar Series

Saltire Software is hosting a Webinar Series highlighting interesting applications of Geometry Expressions from the community.

With Geometry Expressions, you can build larger more complicated models with varied styles, hidden items, and you can save the models.

You can export mathematics in the format for a variety of different CAS systems, along with Tex and MathML.

You can export mathematics as computer source code in a dozen different languages.

You can create your own apps, without programming, as JavaScript or Lua apps

Past Webinar:

Learning Online with GX: Create Your Own Live Online Tasks With GX


Geometry Expressions software, along with the free GXWeb, offer many amazing opportunities for learning mathematics, even beyond their unique blending of constraint-based dynamic geometry and computer algebra. The ability to create Gx documents and then export these to a variety of formats is a powerful feature - the focus in this talk lies in exporting to the web, using HTML5 and JavaScript.

When seeking to create interactive online activities it is demonstrated here that it is possible to go even further - using JavaScript to read properties from the embedded GX applet,and to write to the applet from the web page.

Of course, you might wonder why someone would want to do these things. The examples shown in the Geometry Expressions Showcase demonstrate the power to create interactive assessment/exploration tasks perfect for online learning built around an embedded Gx applet - students can even explore STEM applications using the in-built sensors on their mobile devices!

About the speaker

Dr Stephen Arnold

Dr Stephen Arnold has taught in schools and universities in New South Wales, Queensland and the Australian Capital Territory, where he previously held the position of Head of the School of Education at the Australian Catholic University, Canberra campus. Steve has worked with schools and teachers across Australia, New Zealand, the United States, Europe and South-East Asia, and is a nationally-recognized expert on the use of classroom technologies for mathematics and science.

Over the past decade and more, Stephen worked with Texas Instruments on the development of the TI-Nspire Mathematics and Science Technology platform. These days, his focus is on developing free web-based resources for mathematics and STEM teaching and learning.


May 27th @ 4:00pm PDT, 7:00pm EDT; in Australia - May 28th @ 9:00am AEST.

Past Webinar:

Animating Algebra and Calculus Problems with Geometry Expression and Maxima

Sample Animation

The author of Learning Calculus with Geometry Expressions brings us his love for Color and Calculus to pose some problems from an innocent description to a more complex exercise with both a geometric and symbolic solution formatted together in a signature tableau, suitable for posting. Van believes, if 'a picture is worth a thousand words.' - an interactive animation is worth a thousand pictures!

About the speaker

L Van Warren

L Van Warren holds degrees in Computer Science as well as Aerospace, Aeronautical and Astronautical Engineering. For ten years he was a system's engineer at NASA's Jet Propulsion Laboratory. He was the technical director for the "Earth from Space" image sponsored by National Geographic. His other interests include Biochemistry, Molecular Biology and Genetics which probably attracted him to his current position as Data Scientist, crunching numbers of the pandemic at the University of Arkansas. But one of his favorite hats is teacher, especially of Mathematics. Among the many math texts he's written, Learning Calculus with Geometry Expressions might be the one with which you could learn calculus in a week!


June 3rd, 2:00pm CDT, 12:00pm PDT

Past Webinar:

Connecting Algebra and Geometry: Teaching Proofs with Technology


Teaching reasoning and proofs in high school geometry is one of the challenging tasks that we face today. Can technology help us with this task? In this presentation Dr. Lyublinskaya will share a set of problems that uses Geometry Expressions to support development of students' proofs skills. Use of this technology gives students access to a powerful toolkit for participating in an inductive, exploration-based, learning environment that integrates geometry and algebra.

About the speaker

Dr. Lyublinskaya Image

Dr. Lyublinskaya is a Professor of Mathematics and Education at Columbia University Teachers College. She holds a PH.D. in Theoretical and Mathematical Physics from Leningrad (now St. Petersburg) State University. Irina teaches teachers all over the world. Her specialties include STEM Education and Educational Technology as reflected in her numerous publications on these subjects.


Thursday June 11th 10am PDT, 1pm EDT, 6pm DST

Past Webinar:

Parametric Visualization with Geometry Expressions

parametric sample

Geometry Expressions empowers students to visualize geometry both graphically and symbolically. Using variables, these graphics can be controlled parametrically. Parametric geometry models and apps can demonstrate a wide range of mathematical concepts. The same parametric approach to modeling in Geometry Expressions can be applied to other modeling software, such as Revit, which is used for building design and construction. This talk will be presented in interactive geometry apps, available to follow along during the presentation. Additional interactive apps, documentation, and tutorials offer deeper exploration of the examples presented through individual discovery.

About the speaker

Nick Halsey

Nick Halsey came to Saltire Software as a high school intern 7 years ago. He selected a project to model the Twisted Savonius Wind Turbine. Today he is an Engineer, Composer, and Designer in Portland, Oregon. He designs new building structures and seismic retrofits at KPFF Consulting Engineers. Architecture, engineering, and the built environment are his primary passions; his persistent creative drive also extends into digital works ranging from software (via WordPress) to sheet music, photography, and digital art.


Tuesday, June 16th @ 10am PDT, 1pm EDT, 6pm DST

Past Webinar:

Using Mathematics to Help Cure Hunger, Disease, and Global Warming

Dr. Todd creates mathematical models of simple solar cookers and formulates design questions as mathematical problems. The solution uses a powerful combination of technology and brain power.

About the speaker

Philip Todd Philip Todd first started work on both constraint based mechanics and symbolic geometry as research projects in the Tektronix Computer Research Lab in 1986. He licensed the technology from Tektronix and founded Saltire Software in 1989. Saltire’s initial product, Analytix, is based on constraint based mechanics and is still in use around the globe.

Symbolic Geometry remained a research project at Saltire until advances in hardware speed and memory made a product based on the technology viable in the mid 2000’s. Geometry Expressions was born.

While a computer programmer by trade, Phil is a mathematician by training. Over the last 14 years he has mentored high school interns at Saltire Software through the Portland Saturday Academy, and is proud to have 4 interns working entirely remotely this summer.


Jun 22, 2020 04:00 PM in Pacific Time (US and Canada)

Past Webinar:

Ellipses Inscribed in a Triangle: investigations and proofs using backward reasoning


I was working on some interesting properties of polynomials of the third degree in relation to the Steiner ellipse for several research papers. My aim was to show an approach supported by dynamic geometry and CAS. Focusing my attention on a known property of the Steiner ellipse, I realized very quickly that the first complete proof of this property was only given in 2008 by Phelps and Minda in the AMM (American Mathematical Monthly). Finding this proof really complicated, I started to look for a simpler proof using TI-NSpire (dynamic geometry and CAS). I will present the proof I eventually found thanks to an experimental approach and show how using technology can help researchers bridge the gap between conjecture and proof. We will see that the use of CAS is mostly problematic and that knowledge and brain power is always the core of a real math activity applied to problem solving for researchers or demonstration for teachers. Teachers will discover lots of ideas for research activities to propose to their students at all levels.

YouTube channel: jjdahan

Paper ATCM 2019 Leshan: Steiner Ellipse and Marden's Theorem

Playlist paper T3 2020 Dallas (9 videos): Construction of all ellipses inscribed in a triangle : Blending DGS and CAS within TI-NSpireTM CX Premium Teacher Software

Playlist of this talk in french

About the speaker

Dr. Jean-Jacques Dahan

Dr. Dahan holds a Ph.D. in Mathematics and Computer Science from Grenoble University. He leads the Dynamic Geometry research group at IRES (Institute of Research for the Teaching of Science) at Toulouse. He has taught Math from highschool through college, as well as science education for pre-service training. His work has always involved technology (calculators, software and especially dynamic geometry). The core of his work centers on the use of dynamic geometry for teaching and research. His YouTube channel contains hundreds of videos including resources, research projects with middle-school and highschool teachers as well as some of his talks. His numerous publications cover pure math research and science education all related to dynamic geometry and CAS using Cabri and TI-NSpire software. And now he has offered to show us his techniques using Geometry Expressions. For nearly 20 years he has presented his work at math conferences meetings around the world.


Jun 29, 2020 10:00 AM in Pacific Time (US and Canada)