Friday, June 7, 2013

Goldilocks and the Three Triangles

I was in the middle of a lesson yesterday and was struck with an idea. I am sure others have thought of it, but it was new to me. The focus was to help my students remember what a right, acute, and obtuse angle are so that they can identify different kinds of triangles.

The Goldilocks metaphor came to me when I said that 90 degrees is a right angle. One of my students asked, "Why is it called a right angle?" I jokingly answered, "90 degrees is just right." Then the fairy tale came to mind. 90 degrees is "just right." Acute is the angle that is "too small" and obtuse is the angle that is "too big."

Worked for my students. 

Another part of identifying triangles is the length of sides. My students know equilateral because they hear the word equal in it. They know it means all side are equal length. What was causing them confusion was how to remember the difference between scalene and isosceles. Again, brainstorming with my students to find a mneumonic that works, I came up with two sides are the same length, we have two eyes, Isosceles. If they know equilateral and isosceles, scalene is easy!

Now they need to study the memory devices and practice identifying triangles!

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