Comments on: Geometry – Day 61 – Circles, Sectors, Segments, and Annuli

By: dan

dan — Sat, 10 Mar 2007 06:06:12 +0000

Nope, no sarcasm at all. I just get twisted up on the difference sometimes.

By: e

Sat, 10 Mar 2007 05:15:07 +0000

I note a hint of sarcasm in your response. I’ve noticed before that you seem bit defensive about these lessons. Somebody said that they could understand it since you clearly put a lot of work into them. I agreed, but also thought that since you are so concerned with teaching that you would also be concerned with what you teach. Does it seem like a petty peave to you, this issue of translation vs transformation?

How do you respond to a student who says “I just can’t seem to get this translation/transformation thing right”? Do you say “Oh, well, it’s ok, no worries”? Or is it not ok?

By: dan

dan — Sat, 10 Mar 2007 03:45:02 +0000

Oh, and no one’s outed themselves as r/g colorblind, but, playing the odds, I should probably work on my color selection. Crud.

By: dan

dan — Sat, 10 Mar 2007 03:40:10 +0000

E, I just can't seem to get this translation/transformation thing right. Mr. C, Yeah, yeah, I'm such a fan of limits, both in mathematics and as a logical exercise. I wish I could think of more gentle ways to introduce them. Especially, I would love to derive area of a circle by sending the # of sides of a regular polygon to infinity. I'd lose half the class inside the first slide, but it might be worth it for the sake of the second half.

By: mrc

mrc — Sat, 10 Mar 2007 02:22:17 +0000

First — Love the circle area dissection. It hints at limits, which is nice. I feel like I just saw this demo for the first time very recently, maybe in the NCTM newsletter?

Also, do you have issues with red/green colorblind kids doing your opener?

By: e

Sat, 10 Mar 2007 01:16:23 +0000

In the opener: a) is a reflection. b) could be translation, and it could be a reflection, or it could be translation followed by rotation (many of them), or it could be reflection followed by rotation, or……
More realistic name: usually people refer to a torus as a doughnut. Both are rather questionable. Torus is two dimensional (surface), annulus is one dimensional, doughnut is 3 dimensional.