Tuesday, January 15, 2013

Why is a Triangle a Triangle?

For a long time, young children learned shapes by sight, without regard to attributes (characteristics).  An octagon looked like a stop sign, by golly, and any 8-sided figure that didn't look like a stop sign must not be an octagon.  Standards today, whether they are common core or our Texas TEKS, emphasize defining shapes based on attributes. ANY 8-sided polygon is an octagon.  An octagon is defined as such because it is a polygon with 8 sides.  Period.

Let's look at some of the common core standards:
K.G.2--Correctly name shapes regardless of their orientations or overall size.
K.G.4--Analyze and compare two- and three-dimensional shapes, in different sizes and orientations, using informal language to describe their similarities, differences, parts (e.g., number of sides and vertices/"corners") and other attributes (e.g., having sides of equal length). 
1.G.1--Distinguish between defining attributes (e.g., triangles are closed and three-sided) versus non-defining attributes (e.g., color, orientation, overall size); build and draw shapes to possess defining attributes.
2.G.1--Recognize and draw shapes having specified attributes, such as a given number of angles or a given number of equal faces.  Identify triangles, quadrilaterals, pentagons, hexagons, and cubes.
What are some things you notice?  First, I notice orientation and size.  Be sure kiddos see lots of examples of each of the shapes.  The shapes below are all triangles, although the look quite different.  Geoboards are a GREAT tool for exploring different shapes.

I also notice that both 1st and 2nd grade mention drawing shapes.  How much practice do your kiddos get with that?  Think what a rich exercise it would be to have all your students draw "a five sided closed figure".  Imagine all the different looking shapes you'd get!

Here's a little assessment I made for my 2nd grade teachers.  Click here to grab it. For more information on helping kiddos identify geometric attributes, check out this blog post.


  1. I cannot agree more! My children are fascinated by seeing an eight or nine or even ten sided figure they cannot recognize. Love this!


    1. Love the curiosity of kids! Thanks for sharing, Christen. :)

  2. Why this post can't be any more PERFECT!!!!!!! You are A.W.E.S.O.M.E.!!!!

  3. Thank you, Donna! I always love your explanations and I'll definitely be using this assessment with my second graders. Thanks so much for sharing it!

    1. Thanks, Linda. I really appreciate your comment! :)


Comments make me smile! :)

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