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Exploring and Teaching - Skeptism and Mistakes

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This thread comes from 2 thoughts and if / when you have time I would really appreciate any thoughts on this. Even quick reactions are good.
(a) I read this headline - "Teaching with Skepticism and more ..."    and
(b) I didn't easily see that the diagonals split the rectangle into 4 equal areas and was willing to say so in my video.

I enjoy being skeptical and wondering why things work and whether I can prove them and if not - where they go wrong. I don't mind being confused and trying to figure out what confuses me. How do we bring this into the classroom - into the teacher's and student's psyche? The skepticism and the wanting to wonder, to explore, to prove, to make mistakes and by continuing to test, find and correct our mistakes is important.

"Rich problems" don't do it for me and I don't think they do it for students. Often they take up huge amounts of time trying to understand the text of the problem and not the math.

In contrast, small problems like we are doing here and screencasting and/or constructing with GeoGebra work for me. With screencasting, we talk/show our thinking process. And when I think aloud, I become more conscious of what I am saying/doing and skepticism has a chance to enter my work, i.e. "Why am I sure this is right?", "What facts/formulas am I using?" .
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First let me say that the headline was actually for "media messaging" not mathematics, but it seems to me that we teach math so "boldly".

For example, we state: the ratio of circumference of a circle to its diameter is pi. Like it is the most natural thing in the world. I think it is EXTREMELY odd. and I will bet that the Greeks (or whoever discovered pi) thought God must be having some fun. Firstly, it is odd that it is always the same number, and secondly, it is odd that pi is not a particularly nice number. But we talk about pi like it is a natural number (pun intended).

Also, it took me a while to see (b). I am not giving it away though - it was a wonderful ah-ha moment. I walked around with my folded rectangle in my pocket.   I am relatively certain that in almost any hs geometry class, the teacher would think me slow for not knowing this. (I found that if I teach something over and over the same way - I begin to think everything is obvious.) My point is that I allowed myself to be skeptical, to be confused and then - using my mathematics and logical thinking skills - I worked it out.

Esther and I have been talking (see her page) about the skills that make you successful in life and the fact that these skills don't seem to be encouraged in today's classroom. Jumping in head first, being willing to make mistakes, testing our results and if they don't work, figure out why and fix them.

Re: Square from Diagonal Problem
I asked Steve if we could give a diagonal to a student and ask them to create a rectangle and he said "no" - the non-uniqueness would confuse them.

1. Is confusion bad if we teach them how to logically confront it? (Of course, we must start this process when they are very young.)

And, Cathy was doing her "trying to think like my students". Just looking at the "image", I could NOT figure out why her construction wasn't a square. I finally realized that because the construction was done in GeoGebra, I could follow it (view->construction protocol) - like a screencast. Three points here.

2. I could "see" it wasn't right, but I didn't know why - However, I WANTED to spend the time to find the problem (do our students??)

3. By following the construction protocol, I could say to myself  "Yes, we see the diagonals crossing perpendicularly at the midpoint. That's good. Ahh, C isn't right" and to my student  "Something about C doesn't look quite right. How did you find it?"

4. I see GREAT value in giving this construction as part of the problem and asking "Why isn't this a square?" Why? Because they may go right for the easy construction. Part of learning is recognizing something is wrong and finding out why.

As teachers, we want to help our students learn. To do this we must allow them to make mistakes, but teach them to test their results. With screencasts and GeoGebra, finding where they are not testing their thinking is easier both for us and for them.

I tend to go on and on....

 

Esther Allerton's picture
Esther Allerton
Mon, 2011-01-31 17:46

b) I didn't see it at first when I read it. In fact, I didn't believe it - maybe I'm a natural born skeptic ;-) I tried to find a way to 'visualise' it using geogebra and that geomovie software but couldn't figure a way that represented what I was 'seeing' in my mind, but what I was 'seeing', after a bit of fiddling, was that the diagonals split the rectangle into two pairs of disimilar triangles. There was a relationship between the pairs though - the height of any triangle was always half the base of the other, so when you do 'half base times height' on either type of triangle, you always end up playing with the same set of numbers. I think...

I need to find a way to bring what I'm seeing to life so you all can see it too. I'm not sure if geogebra can do it - I want to draw a rectangle, chop it up into four triangles and then be able to grab those triangles and move them around and put them back a few times.

In fact, ideally I'd start off playing with a square, then moving up to a rectangle, which is also what I think should happen in the 'square from a diagonal' problem. I think you could get students to see how many different squares they could make from a diagonal (they'd soon discover it was only one) and then extend it by asking them how many rectangles they could make from the same diagonal. They'd soon either get fed up of counting or decide it was infinite. That way, I don't think any of them would get confused, but they would be involved in discovering something.

I think maybe the difference in the approaches is that instead of asking them to prove something (ie assume it's right and find out why) you're asking them to discover something, and that way they might be inspired to figure out why.

Linda Fahlberg-Stojanovska's picture
Linda Fahlberg-St...
Mon, 2011-01-31 18:52

Yes – and wasn’t that moment perfect when you saw the relationship! I loved it. I went around smiling for hours.

1. I am thinking about the chopping up too. I think I will chop up the fourths of squares first.

2. I like the "How many squares can you get from this diagonal?" question.

3. I VERY much like the word “discovering” and not "proving".

Re: Folding + GeoGebra - I try to remember to test things out at least 2 ways. Doing it by hand and with GeoGebra has helped me. I made a mistake by hand (our problem in week 5) and was positive something worked. I spent hours making movie, adding sound, captioning etc. Five minutes after I posted it online and broadcasted, I tested it in GeoGebra and it did NOT work. I really did learn so much more from the mistake (math things - not to test things before I post; I am never going to learn that :-) ).

Esther Allerton's picture
Esther Allerton
Mon, 2011-01-31 23:15

I posted up a screenshot of a rectangle split into four triangles along the diagonals, with two of those fourths split again into eighths. I think you might find it interesting - it's suddenly *obvious* why those fourths are the same area, it's because the eighths are congruent!

http://homeschool-math.wikispaces.com/Fiddling+with+Math+-+Virtual+Manip...

Linda Fahlberg-Stojanovska's picture
Linda Fahlberg-St...
Tue, 2011-02-01 18:53

Challenge - In GeoGebra, draw a line segment. Now construct a rhombus where one diagonal is this line segment and the other diagonal is TWICE as long. Think about all the different things you can find out about this rhombus (area, perimeter, angles). (This kind of relates a whole bunch of things we have done.) http://en.wikipedia.org/wiki/Rhombus

Linda Fahlberg-Stojanovska's picture
Linda Fahlberg-St...
Wed, 2011-02-02 00:56

The above challenge is not quite as good as I had hoped (you cannot get the angles without trigonometry). I have NOT tried this next challenge so don't know how difficult it is to construct.
NEW CHALLENGE: Draw a line segment. Now construct a rhombus where one diagonal is this line segment and the SIDES are TWICE as long (as this diagonal). If we can construct it - this one has famous angles.

Linda Fahlberg-Stojanovska's picture
Linda Fahlberg-St...
Wed, 2011-02-02 16:40

Hopefully 3rd time is the charm. Here is the challenge: http://www.youtube.com/watch?v=5vRd5dKQQvU (you need trigonometry in the others - this one is just pythagoras')