Geometry – Week 1 – 2007

Search Engine Chum

  1. first day activities, icosahedrons
  2. points, lines planes, collinear, congruent, congruency
  3. midpoint formula
  4. angles, protractors, acute, obtuse, pool table geometry
  5. free powerpoint geometry lesson plans


  1. Here it is, more of the same, this time in a weekly format, which both the author and the readers might find more manageable.
  2. It has always been the goal that I reuse every minute I spend working on school outside of school. Yeah, I spend ample time revising but I’ve never made a worksheet or a lesson plan that wasn’t waiting for me the next year in some kind of digital storage. If anybody else gets anything out of these, it’ll make my time feel even less wasted.
  3. Please comment. Nitpicking (“those figures ain’t drawn to scale”) will receive a polite “thanks,” a revision for future drafts, but little else. Substantive critiques – alternate methods, exciting investigations, effective strategies – will receive a lot of gratitude.
  4. We didn’t touch a syllabus the entire first week. I alluded briefly to my two big-time class rules (respect the speaker, always participate) but didn’t go near my usual enforcement methods (the one minute board). I have no idea what this means, only that it’s potentially paradigm-wrecking, something that circles issues of positive expectation and the teacher-student relationship. I’m confused.
  5. The protractor on day four kinda swoops in under the angle. Some kids thought that was pretty cool.


  1. Keynote (which choosey moms choose)
  2. PowerPoint
  3. PDF
  4. Interactive QuickTime


  1. I’m greeting at the door. They come in and something is waiting for them. This sets the year off right as far as I’m concerned.

  2. We use the instructions laid out on page 39 of the attachment. Offer them one homework or the other: hold up a stack of handouts or tell them they have to make the icosahedron. As they’re pondering their options, start the timer. Freak out time.

  1. Michael & Jessica

  2. We’re laying the groundwork for geometry right here. Setting ourselves up so we can talk this language.

  3. Talk to a neighbor, a friend, a loved one, or yourself. Give us two examples of points, lines, and planes.

  4. Which tennis balls are coplanar? Which sets of three are collinear?

  5. You wanna say that two segments are congruent, you mark it in with cut marks. You wanna KEEP saying that segments are congruent, you keep on marking it up.

  1. Free food for life.

  2. Ask people to tell you what the points are. Ask them to put down what looks to be about the midpoint. Write the coordinate down. Decimals are okay.

  3. Have them notice that it’s two over, three up, two over, three up.

  1. French fries.

  2. Referencing a slide from earlier in the week. Again, we’re laying foundation so we can talk about shapes and figures.

  3. Talk about acute vs. obtuse here.

  4. Registering for our online course software.

  5. The section on billiards: 16:40 through 22:08
I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. He / him. More here.


  1. Dan,

    Your work is nothing short of genius. You really must have a lot of energy to create such knockout presentations day after day.

    A couple of technical questions, if you don’t mind. These may seem dumb, but …
    1. How long are your class periods?
    2. Do you use an LCD projector?
    3. Is it ceiling-mounted?
    4. Are all your school’s classrooms equipped thus?
    5. When you present your slides, do you turn out the classroom lights?
    6. If you turn out the lights, do students sometimes get a little drowsy?

  2. Nah, these are good questions. Here’s my shot at some answers:

    1. We do five hours a week split up into three periods, one regular period and two block periods. The blocks are two hours long. You’ll know a particular lesson is a block period if you spot the Break / Show and Tell combo.
    2. I use an LCD projector, supplied by my school. If I ever leave this school, I will be so ballsy as to make an LCD projector a condition of my hiring. I can’t teach at this level without one.
    3. No.
    4. No.
    5. Sometimes. If the projector and bulb are good enough and my slide-text large enough there’s no need for this.
    6. Maybe a little. Negligibly so, though. My students’ drowsiness, whether the lights are off and I’m moving through a lesson or the lights are on and they’re doing book work, depends more on my ability to stay mobile, issue encouragement, and show them success than something like lighting.

    Good questions, thanks.

  3. Really, really dumb question…so, I’m trying the gradient thing. Looks great on macbook, yet each looks gray on-screen. Any ideas? suggestions of tech people…keep trying different colors

  4. Projector calibration issue. Wish I was around to tweak settings for you. I’d end up mashing buttons same as you, though.

  5. Dan, Choosy mothers may choose Keynote, those of us given free laptops and software by our district live with HP and MS. A projector is a condition of my employment even at primary level. Digital projectors, they’re not just for college/high school classrooms anymore.

    Big cheer/suggestion: I love day 2 slide 2 Notes where you use a story metaphor to explain points. You then go back to non-narrative explanations of the other terms. The use of that analogy is FANTASTIC! Don’t STOP! Try to mix it in more in your definitions.

    There. That’s it.

  6. You mean the “no friends” gag? Hm. It got a chuckle (and a buncha eye-rolls) but I hadn’t pondered its significance to math comprehension until now.

  7. Looking at it again, it was more than a metaphor, it was actually a personification. You know when the kids are laughing they are often remembering it better, so I hope you take that as a cue to do it more and often, lol.

    You did a good language arts teacher thing there. It’s not separate stuff anywhere except in education (especially comprehensive high schools).

  8. I like your opner. Seems like a good way to get the students to use the time from they get it untill it quiet down so the class really can start. I guesse it also speed up the process to quiet down. Some questions about them.

    How much time do you spend on them? (about)
    Do you collect the work?
    Can they work together?


  9. Having something ready for them on the board certainly speeds the quieting down process.

    We spend anywhere from 5 to 10 minutes on each. I’ll walk around about 7 minutes in and start stamping openers depending on how much work they’ve completed. If they’ve tried every problem I stamp it.

    I collect the opener sheets (and all the stamps) at the end of two weeks.

    They can work together but I want them to know what they themselves know first.

  10. That’s a good lesson plan for geometry. I’ve been teaching it for a number of years but am always learning new techniques and way to make it more interesting to the students.