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Monday, March 26, 2007

point symmetry

So tonight we've learned point symmetry.



Thank God my Sudden Math Learning Curve has speeded up.


Moise and Downs

We were sitting at the dining room table flipping through our dozens of math books, looking for point symmetry.

Ed found a point symmetry lesson at the very end of the Moise and Downs geometry text.

C. is in 7th grade; Moise and Downs was a sophomore text when Ed was in high school.


sink or swim

This is Darwinian gatekeeping, pure and simple. An expensive sorting machine.

C. can learn this stuff.

He can learn it easily.

But not in this class, not with this curriculum & this pedagogy.

He'll get through because we'll reteach the course at home. Down the line the school will take credit for his high SAT math scores; in the meantime we'll be identified as helicoptering lunatics and Huns.


I guess I can live with that. (may have to hit refresh before page comes up)


wit and wisdom
eSchool News on Singapore Math
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2 comments:

  1. AnonymousMarch 26, 2007 at 7:18 PM

    We've got a 1966 Moise and Downs.

    Compare and Contrast the TOC.

    I wish I had put up some sample problems and then we could really compare and contrast:

    http://www.oplink.net/~adrian/moise.html

    If something looks interesting to you, let me know and I can scan it from the book.

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  2. Rudbeckia HirtaMarch 27, 2007 at 5:58 AM

    To teach any of these symmetries, you just need the right manipulative: overhead transparencies.

    You make two copies of each image: one on regular paper, one on overhead transparency. You start with both copies lined up exactly (the transparency over the paper).

    If you can slide the transparency and still have the details of the image line up, then it has translation symmetry. (You have to use your imagination about the pattern going on forever -- or at least past the edge of the page.)

    If you can rotate the transparency and still have the details of the image line up, than it's rotation symmetry. (I believe that "point symmetry" is a rotation symmetry of 180 degrees?)

    Pick the transparency up and flip it over and things still line up? Reflection.

    Flip it over then slide (like with a pattern of footprints: left- and right-handed version of the image staggered): Glide Reflection.

    I teach this in my class sometimes; I keep telling people that I'm teaching 7th grade math. ;)

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