Day 26-27: Circles

Yesterday and today we looked at angle and arc measures in circles. I give a whole bunch of practice on these types of problems – central angles, inscribed angles, angles formed by secants and tangents and chords…It’s a lot for them to distinguish in two days but with all the practice most of them get it.

Yesterday didn’t really have too much excitement…today was the opposite because we played another awesome review game. It basically is Grudgeball but I do have a few adjustments. I introduce it with talking about Mario Kart’s battle mode – I talk about how I love Mario Kart but I hate playing the battle because my strategy is always to hide out because I hate getting my balloons popped. We talk about strategies of the game for a minute or so (further confirming to some students how nerdy I can be) and then I tell them they’ll be playing a version of this today. When I had an interactive white board, I would actually project balloons for each team and then students would slash or un-slash a balloon. This time, I just drew X’s and let groups erase or redraw an X. I gave everyone a pretty extensive review packet and said that for every two that the entire group shows me is correct, they could pop a balloon from another team, and for every three they show me correct they could blow up one of their own balloons. The students asked to do this for every review, but then thought of Mathketball and said we should split between the two. It really was engaging to all of them and I believe it helped them review as well. Some other notes:

  • I don’t let groups get multiple pops or blow-ups at a time – they either show me two or three and then I say “correct” and give the marker or eraser or “at least one part is incorrect” and then go away from the group. This keeps groups from just saving all of their problems for the end.
  • I had each group start with three balloons (X’s) and they could never have more than three. I wasn’t sure how the game would go over with high school students but next time I would give more balloons.
  • In the final five minutes, I tell groups that I will walk around to the groups one final time at the end to see if they can earn their last pops/blow ups. I take note of what they’ve earned then but don’t let the students go up to the board for this. When I’m done going to the groups, I then go randomly through the groups and tell the class how they want to use what they’ve earned. So it could be that there looks like a clear winner at the end, but in the final minute all groups wanted to pop that one groups remaining balloons and the game totally changes. I like this because it doesn’t allow groups to just slack off when they see they are winning or losing.
    All groups started with 3 “balloons”.

    Groups 3 and 4 were winners! It doesn’t look like much changed but there was so much change during the game…should have taken more pics.

I also had been given this clever cheat sheet for finding angles in a circle called “Dude Where’s My Vertex?” and I’m attaching that below.

La vengeance est amusante en classe!

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3 thoughts on “Day 26-27: Circles

  1. I love the “dude where is my vertex” idea. I used to use that thought until I realized there was one “on” situation that didn’t really work. I believe it is the secant/chord “on” situation. The only way to find that type of angle is to find the supplement of it first and then subtract from 180. Have you come across this. My students would always get this wrong because they would take 1/2.

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