NCTM Comes to Music City

The National Council of Teachers of Mathematics held a regional conference in Nashville, TN last week. Since I live in Music City, this was too good an opportunity to pass up! I’ve attended several NCTM conferences, both national and regional, and this was by far the best and most technologically savvy one.

To begin, I installed the conference app on my phone, which made planning and organizing my experience a breeze. It synced the sessions I wanted to see with my calendar, so I received reminders and updates for each one. The app also promoted interaction among attendees through its Activity Feed. We could also keep up with what was happening via Twitter using the hashtag #NCTMregionals.

The first session I went to was “Hands On Trigonometry”, by Elizabeth Petty. She led us through a lesson on the unit using paper plates and twizzlers to demonstrate what a radian is. We then folded the paper plates in half to create an x-axis, then thirds to mark the 30 and 60-degree points on the circle. It was an excellent example of using a hands-on activity to reinforce a difficult math concept.

The next session, “Keeping It Real: Authentic Real-World Math Lessons”, was presented by Ginny Stuckey of Mathalicious. Their mission is to develop lessons that use real-world data and situations to spur critical thinking in students. The lesson Ms. Stuckey demonstrated involved how municipal fines can quickly become impossible to pay off for low-income offenders.

Next up was one of the best sessions of the conference, “Using Manipulatives and Investigations to Teach Geometry”, by Christine Mikles. Ms. Mikles uses the CPM Geometry text, which is full of hands-on activities. Here’s an example of using two mirrors and a protractor to learn about central angles in regular polygons:

Polygon with mirrors

The last session I attended on Thursday was “Slices of Calculus”, by Nina Otterson. As a veteran calculus teacher, I was very excited to learn a new way to teach how to calculate the volumes of solids of known cross-sections. Ms. Otterson’s approach makes a lot of sense: she has her students learn what ratio of a square’s area is an equilateral triangle, an isosceles right triangle, and a semicircle. Then, they find the volume of the solid using a square, which is easy, and apply the appropriate ratio. Her students build models of each type of solid. Here’s one I built using equilateral triangles whose base is a pair of intersecting parabolas:

Solid with Triangle cross-sections

Friday’s first session was “The Math Department I’ve Always Wanted: Twitter As My PLC”, by Michael Felton. It was an excellent presentation on how math teachers can use Twitter to ask questions of other teachers, get great ideas for lessons, and get feedback on their own lessons. Michael is part of the “Math Twitter Blogosphere” (#MTBoS on Twitter), where some of the most innovative teaching is being developed today. If a teacher needs some ideas on how to teach practically any math topic in a creative way, he or she can find it at MTBoS.

Next, I went to a session sponsored by CPM (College Prep Mathematics): “CCSS Math Practices? Trust CPM’s 25 Years of Writing Experience”. This company is a nonprofit textbook publisher run by math teachers. Their series of books stresses the importance of hands-on explorations to teach math concepts. I was very impressed with the passion and excitement of the teachers who use these books.

Finally, I went to another session by Michael Felton, “Desmos and Modeling”. I’ve used Desmos‘ online grapher for several years now (I even did a presentation on it at a TAIS conference last year). They have moved far beyond a simple function grapher, though. Their site now includes all kinds of activities that teachers can use in the classroom. The one Michael demonstrated involved matching transformed sinusoidal curves, and it was a lot of fun. Go to to see all the fantastic lessons they offer. Teachers can also keep track of students’ progress as they work through the activity.

All in all, an excellent conference. It is fascinating to see how social media is transforming teaching, and how much teachers are trying to incorporate active learning into their lessons. I figure a conference is worthwhile if I can take home at least three good ideas/lessons/activities from it. After this one, I have more than dozen to try out with my students!


A Balancing Act

In Geometry, we are learning about circumcenters, orthocenters, and centroids of triangles. Geogebra is a nice tool to use to explore how the medians, perpendicular bisectors, and altitudes are concurrent respectively, regardless of the shape of the triangle.

Here is a screenshot of the centroid, which is the intersection of the medians of a triangle:


Here is the circumcenter (the intersection of the perpendicular bisectors), with a circumscribed circle:


And here’s the orthocenter, which is the intersection of the triangle’s altitudes:


A very nice property of the centroid is that it is the exact center of gravity of a triangle. Here’s a brief video of one balancing on a paper clip:


Embedding Interactive Graphs in Haiku

I’m a big fan of the online graphing calculator at My students and I use it all the time instead of graphing calculators because it is so much faster, and it is easier to enter functions. And now I just figured out that teachers who use Haiku can embed interactive graphs into their Haiku pages!

First, create a function with sliders. For example, in the function pane, enter y = m*x + b. Desmos will automatically ask you if you want to create sliders for m and b, so click “All”.


Next, copy the embed code Desmos provides by clicking on the “Share” button at the upper right (you have log into Desmos to access the Share feature).


Now go to the Haiku page where you want to embed the graph. Click “Add Content Block” and choose “Embed the Web”. Paste the code into the yellow box:


Haiku will say it doesn’t recognize the code, but go ahead and click “OK”. Give it a title and place your content block where you wish, then hit “Save”. You should now see your Desmos graph in its own content block. When your students click on it, it will load a fully interactive grapher!