When Sketchpad is Wrong

Last week we went into the lab to play do an investigation with Sketchpad. The task was to create various polygons, measure the angles in each, and calculate the sum of the interior angles. They were then to formulate a “rule” for the sum of the angles as a function of the number of sides.

Then Sketchpad made a mistake.

“Mrs. B, I know this thing is supposed to be 360. Sketchpad isn’t working.”

I know they’ve “learned” how to name angles in middle school. We talked about it before we went into the lab. Doesn’t matter. I think they think math teachers are just really picky and it doesn’t truly matter.

Then Sketchpad is “wrong”. Then I get to have great discussions with a few individual students.

Then these students get to help those working next to them.

I love Sketchpad.

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5 Responses to When Sketchpad is Wrong

  1. David Petersen says:

    The third angle says CDB not CDA as needed. Is that intentional to make it “wrong?”

  2. Jackie says:

    Uhm, well, that’s what the students did. Not all of them. But too many. Hence my love of Sketchpad for reinforcing the importance of properly naming angles.

    Which I apparently didn’t covey well. Sorry.

  3. Richard says:

    David, I think what she was saying is that students produced that sketch and were quick to conclude that the software was faulty. This brought up a good opportunity for discussion/learning.

    “Hmmm…. That’s strange. Why don’t you compare your results with that group over there…”, etc.

  4. Kate Nowak says:

    That’s nice!

    Sometimes, though, I’ve noticed Geogebra really is wrong…angles would sum to like 361, or alternate interior formed by parallel lines would not be equal but 1 degree wrong. It was a rounding thing. We had to stop having it round to the nearest integer.

  5. Samir says:

    This was a valuable experience for those kids. Technology gives that benefit to students of having instant feedback and makes learning experiences more memorable. I bet those kids next time will first go back and check whether they named the angles properly if the angles do not sum up to 360.

    Kate’s point is well taken too. However every technology has its specific quirks and wants you to provide the input in a specific way. Garbage in, garbage out – my teacher used to say for calculators. Learning that is also a valuable lesson for kids. Maybe teachers should try to know the technology tool really well before deciding to have their students use it?

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