The paper discusses technology that can help students master four triangle centers -- circumcenter, incenter, orthocenter, and centroid. The technologies are a collection of web-based apps and dynamic geometry software. Through use of these technologies, multiple examples can be considered, which can lead students to generalizations about triangle centers.

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### J. Vince Kirwan and Jennifer M. Tobias

A task using multiple representations helps students write explicit algebraic equations.

### Michael Tamblyn

A wonderful experience occurred in a class that I was teaching recently. It was a precalculus class, the last period of the day. The local university had brought over its cadre of preservice secondary school mathematics teachers to observe my class, so there were twenty-four additional eyes on me that day.

### Erik Jacobson

Table representations of functions allow students to compare rows as well as values in the same row.

### Alison L. Mall and Mike Risinger

Our favorite lesson, an interactive experiment that models exponential decay, launches with a loud dice roll. This exploration engages students in lively data collection that motivates interest in key components of the Common Core State Standards for Mathematics: functions, modeling, and statistics and probability (CCSSI 2010).

### Victor Mateas

Economics can be an avenue for teaching such algebra concepts as graphing curves, writing linear equations, solving systems of equations, and shifting graphs.

### Douglas A. Lapp, Marie Ermete, Natasha Brackett and Karli Powell

Algebra involves negotiating meaning between the worlds of mathematical ideas and the symbols that represent them. Here we examine classroom interactions and explorations as they relate to the connection of these worlds through the use of dynamically connected representations in a technology-rich environment.

### Courtney R. Nagle and Deborah Moore-Russo

Students must be able to relate many representations of slope to form an integrated understanding of the concept.

### Natalya Vinogradova

Using estimation helps increase numerical fluency and gives meaning to large numbers.

### S. Asli Özgün-Koca, Michael Todd Edwards and Michael Meagher

The Spaghetti Sine Curves activity, which uses GeoGebra applets to enhance student learning, illustrates how technology supports effective use of physical materials.