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.




6 comments:

  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!

    Christen

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

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

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  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!
    Linda
    AroundtheKampfire

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

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Comments make me smile! :)

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