# Geometry Right Triangles unit project: Barbie Zipline Day 2

Students sat with their partners from Barbie zipline day 1 and we begin by reviewing the scenario and their calculated flagpole height.

Next we discussed how this zipline will work. I used a string and a binder clip to make a model zipline, using a very steep slope for the zipline and I asked students to predict what would happen if Barbie came down a zipline like this.  They agreed that she would fall too fast and get hurt. Next, I held the string almost horizontal and asked how this zipline would work – and students agreed that she would get stuck or mover too slowly.

I explained that the goal for this day is to use a model in class to determine a plan for Barbie to zipline down safely from the top of the flagpole. By the end of class, students had to know what angle of elevation they planned to use and how far from the base of the flagpole they needed to place the end of the zipline.

This day felt a little chaotic, but students did end up finding errors in their measurements by verifying their calculations in a variety of ways. The worksheet below incorporated a range of geometry topics including:

• Pythagorean Theorem
• right triangle trigonometry to calculate lengths
• inverse trigonometric functions to determine angles
• similar triangles

Tomorrow, we test our calculations outside on the the flagpole.

# Geometry Right Triangles unit project: Barbie Zipline Day 1

I have seen posts about Barbie zipline on occasion over the past few years. I’ve avoided the lesson because it seemed like a lot of advance prep work and typically I don’t allow enough time plan this far ahead and work through constructing a zip line trial run to make sure it all works in advance. To keep it completely real, I also hadn’t seen any description or resources that I thought would fit my classes well. But I found myself approaching the end of a right triangle unit in geometry with 2 full block periods mapped on my unit plan labeled “Right triangle synthesis project – need to create.”

This is my first semester with a full time apprentice teacher, Eric, so I have help and some new motivation to make this a fun project for everyone this time too. This time of the school year, with short days, cold temperatures and no end in sight, it seems a lot of students appear pretty bored with school and many of the staff here are also struggling. I really just needed to lighten things up for the students and myself. The next logical thought: Queue Barbie and high quality pulleys.

### Day 1 (80 minutes): How tall is the flagpole?

#### The set up

Randomly assign teams (I used pairs)

Introduce the activity with this fantastic video from Jed Butler:

We leaned heavily on Jed’s blog post and started with the activity guides included in his post, modifying them a little to incorporate his thoughts on how the lesson could be improved and our learning goals.

1. I like having students select a team name because it forces them to talk to each other before they being working with content. It increases collaboration and breaks down barriers with a safe opening topic for conversation.
2. Given the image below, use Mr. R to estimate the height of the flagpole. This led to students getting rulers and measuring on the image and a rich discussion on whether 4 inches is the same as 0.4 feet.

3. #### Discussion

• Eric: What are some ways we could find the height of the flagpole?
• student: climb up the flagpole?
• student: find the angle?
• Eric: What angle?
• student: The angle of elevation?
• Eric: Where does the angle of elevation go (sketches diagram)?
• student: Do we know how tall Ken is?
• student: Are we Ken in this situation?
• Eric: What can we measure?
• student: You could measure the distance from the flagpole to the person.
• student: We could use that angle tool thing that Mrs. B carries around.
• student: oooohhhhhh. yeah.
• Eric: How could we use that? What else would we need to measure? Would we all have the same measurements?
• student: The hypotenuse!
• student: oh! So we could use tangent.
• Eric: I want you to measure two different times, switching roles. Why do you think we should do it twice?
• student: To see if we get the same answer?
• Eric: Will we all get the same answer?
• Student:  No.
• Eric Why not?
• student: Because it is not exact, but they should be really close.
• Eric: Work with your group and make a plan before we go outside.

#### 4.  Measure & Calculate

Outside measurements, then back in for calculations, using this sheet from Jed Butler’s description as a guide.

Favorite question while measuring angles outside:

• student: Is it possible to get the same angle of elevation if may partner and I are different heights?
• Eric: What do you think?

5. Enter both of your calculated flagpole heights into the google form (accessed using a bit.ly address from their cell phones).

#### 6.  Justify flagpole height

Project the spreadsheet from the google form as students enter their flagpole heights.

• Eric: We don’t know the actual height of the flagpole. Here are all of your calculated heights. We need to determine what number to use as the height of the flagpole. What are some was to analyze data?
• students: average, mean, median, outliers, graphs, range…..
• Eric:  Determine what height you believe the flagpole is and use one or more of these measures to justify your conclusion.

Day 2: Design a model and calculate angle of elevation, zipline length, and ground distance.

# Definitions in Geometry update

I blogged a few years ago about starting geometry with developing definitions. I’ve made some changes since then, and I have additional ideas for next year that I want to remember.

I’ve found it more useful to start the school year introducing geometry as art, and developing a need for definitions as students struggle to describe the process to create their designs.

Once there is a need for developing agreed upon definitions for terms, I want to use this video to motivate how and why definitions develop:

To make a definition is to highlight and call attention to a feature or structural property. Historically this comes out of working on a problem, not as a prelude to it. The point is you don’t start with definitions, you start with problems. Nobody ever had an idea of a number being “irrational” until Pythagoras attempted to measure the diagonal of a square and discovered that it could not be represented as a fraction. Definitions make sense when a point is reached in your argument which makes the distinction necessary. To make definitions without motivation is more likely to cause confusion.

– Paul Lockhart, Lockharts Lament (p.22)

Then, students will develop their own terms and definitions (We ended up with of holes, tubes, and bubbles – you can see the fun thread here.) and we can see how complete it is by trying to classify different objects: a sock? a slice of Swiss cheese? a block of Swiss cheese? etc…

We may engage in some form of Attacks and Counterattacks to help students refine their definitions as the situation requires.

After this introduction of what definitions are and how they work, I will use examples and counterexamples for students to work in small groups and develop definitions of other geometry terms, as described here.

# Two Kinds of Simplicity

I have been trying to use CPM’s new Precalculus textbook as a guide for my pre-calculus class.  During my planing period, I opened to the next lesson to try to put together a plan for my upcoming class.

I only had about one hour to prepare for this class period.

This was the opening prompt:

#### but is overwhelmed by the fractions within a fraction. Work with your team to help Gerrit write an equivalent expression that is a rational expression instead of a complex fraction. Be ready to share your strategies with the class.

I approached this task thinking about the 5 Practices for Orchestrating Productive Math Discussions. I worked through simplifying the complex fraction in different ways, trying to anticipate different student approaches.

I stopped to think about how this would work with my class:

• I thought back to when I addressed this topic last year – and how poorly it went. Students were frantically writing steps to memorize procedures. Although I am experienced enough to avoid saying “copy-dot-flip” or “invert & multiply“, I know this is how my students learned to divide fractions and it is how they approached these problems.
• I decided I did not want to teach this the same way this time.
• I considered just doing the lesson as described by CPM because I really didn’t have much time to plan and it was good enough. They are HS seniors. I can’t change their perspective on math and learning at this point – right? I tell myself this sometimes. To just keep it simple, but I never listen.
• I read Dan Meyer’s blog post “If Simplifying Rational Expressions Is Aspirin Then How Do You Create The Headache?” I pictured myself asking students to evaluate a complex expression for specific values and whether or not they would be surprised (or even care) if I could evaluate the expression quickly. They have been beaten down by math for most of their lives. I thought this would just be another instance where a math teacher made them feel less competent, and that did not seem like a productive way to pique their interest.
• I thought about when I recently re-read Lockhart’s Lament, especially this part:

“I don’t see how it’s doing society any good to have its members walking around with vague memories of algebraic formulas and geometric diagrams, and clear memories of hating them … Mathematics should be taught as art for art’s sake. These mundane “useful” aspects would follow naturally as a trivial by-product.”

• I thought about Tracy Zagar’s session that I recently attended at ATMNE’s Conference  where she talked about how connections through multiple representations made explicit can help students to develop understanding. Tracy also asked participants to think about related topics, often taught separately resulting in learners thinking of math topics as separate concepts. We identified related math topics that are taught separately such as:
• graphing lines: f(x)=mx+b and transformations of functions f(x)=a f(x-h)+k
• similarity and slope
• fractions and division
• I thought about Richard Skemp’s article, Relational Understanding and Instrumental Understanding, and how I could help my students see the simplicity and beauty in simplifying complex fractions.

“There are two kinds of simplicity: that of naivety; and that which, by penetrating beyond superficial differences, brings simplicity by unifying.”

At this point I was losing valuable planning time, but I decided it was more important for me to make sense of dividing fractions for myself, and help students to experience the joy in understanding, than it was to have a flawless detailed lesson plan, so I found and worked through Graham Fletcher’s  Making Sense of Invert and Multiply.  During my lunch, I created and thought through as many cases of dividing fractions as I could come up with. Then I selected a few to use with my students.

I decided against starting with the opening question provided in CPM’s textbook above, I thought I would close with that question.

I decided to open the lesson asking students to think about and share how they would represent the number of groups of 1/2 that are in 3/4. Instead of beginning my class with these learners feeling intimidated and overwhelmed, they were curious.

Students discussed and compared representations, made connections and got genuinely excited at the silliness of being in a college credit pre-calculus class and that we were making sense of fourth and fifth grade mathematics. Mid-discussion, one high school senior yelled “I am in 12th grade and I just now understand how dividing fractions works!” Shaking her head with a mix of frustration towards how math is taught and satisfaction that she understood division of fractions.

Once they were ready, students worked in pairs on whiteboards to think through CPM’s opening question. They took time, consulted and corrected each other and all ended with the same simplification in different ways. Then the craziest thing happened:

They asked me for more complex fractions to simplify!

# Understanding systemic segregation in schools starter pack

I recently attended a lecture by Kelly Wickham Hurst about systemic racism in America’s School system. The following is a combination of my notes from her lecture as well as a few resources that really helped paint a comprehensive picture for me of the current state of schooling in America.

• When the Supreme Court decided on the case of Brown vs Board of Education mandating that schools be desegregated, wonderful black schools were closed and over 30,000 competent, qualified black teachers and administrators were fired. Partially as a direct consequence of this action, here is what students and teachers in American public schools currently look like, according to APM reports:

• Malcom Gladwell has a great podcast called Revisionist History, and last season it included an incredible episode about the negative impacts of Brown vs. Board of Education:

The Brown v Board of Education might be the most well-known Supreme Court decision, a major victory in the fight for civil rights. But in Topeka, the city where the case began, the ruling has left a bittersweet legacy. RH hears from the Browns, the family behind the story.

• Adam Ruins Everything made this 6 minute video that explains and summarizes the impact of red-lining in creating segregated suburban communities:

• Nikole Hannah-Jones is a force. She was recently named a MacArthur Genius Fellow for 2017, partially as a result of this series of podcasts:

Right now, all sorts of people are trying to rethink and reinvent education, to get poor minority kids performing as well as white kids. But there’s one thing nobody tries anymore, despite lots of evidence that it works: desegregation. Nikole Hannah-Jones looks at a district that, not long ago, accidentally launched a desegregation program.

• The second episode in this series looks at Hartford, CT school district’s efforts to integrate and includes and an interview with then Secretary of Education Arnie Duncan:

Last week we looked at a school district integrating by accident. This week: a city going all out to integrate its schools. Plus, a girl who comes up with her own one-woman integration plan.

• Be aware of your own biases. We all have biases, but increasing our awareness of them can help up to make conscious adjustments to ensure that our prejudices have minimal impact on our decisions. Try taking Harvard’s implicit-association tests.

Where do we go from here? Below are the ideas presented by Kelly Wickham Hurst at her talk as well as a link to a article she wrote in 2016 on the topic.

Being Black at School: 10 Things Schools Can Do Today for Black Students

My biggest takeaway from Hurst’s talk was to stop getting stuck analyzing data and start acting and having hard conversations. This requires you to critically consider who is served when implementing school and local polices with which you may have been participating and complying in for your whole life.

When you see something in schools that marginalizes a population, or a well intentioned policy that you recognize as being harmful to students, do something. Don’t just passively comply. Speak up. Change the rules. Run up the flagpole and take that shit down.

# Promoting whole class discussions with pre-written questions

I am starting the school year in precalculus having students develop both their collaboration skills and their ability to model real world scenarios with mathematics. It is the beginning of the school year and many learners are still a little uncomfortable with each other and with their confidence in math class. I wanted to have a productive class discussion, and to make students feel safe to engage in dialogue around the content. I decided to create a discussion that appeared natural as a gateway to get some of the less confident learners engaged in the content.

At the start of class I presented a scenario to optimize by modeling with mathematics. Learners worked in randomly assigned small groups to develop an optimal solution and then, in the last 20 minutes of class, each group was to present their solution and reasoning. I wanted the learners in the audience to ask challenging questions to learn more about the groups thinking after each presentation.

Here is what I did:

While listening to learners work on a task in small groups, I circulated, listened, and wrote questions for each group on separate index cards. I was also thinking about how to sequence their presentations based on their approaches as described in the book, 5 Practices for Orchestrating Productive Math Discussions.

When each group was setting up to present, I would discretely hand the questions written on index cards to a less confident learners. After the group presented their thinking, I would ask, “Does anyone have any questions for this group?”

The learners would look around nervously in an awkward silence while I glared uncomfortably at a learner with an index card. Eventually, uncomfortable with the silence, the learner would ask the question on their card. Then, the presenting group would respond, which led to genuine student questions, thinking and further discussion.

By the last groups presentation, many of the learners seemed comfortable to ask questions and engage in thoughtful whole class discussion!

# AP Computer Science Principles Blog List

This is my first year teaching AP Computer Science Principles. I am super excited to bring the first AP class to my tiny alternative high school. I attended AP training through code.org’s TeacherCon in Phoenix, AZ in July 2017. It was very helpful and so far, I am enjoying using their curriculum.

I created a new blog to use to post a short daily post for each day of my AP CSP class. You can access that site here.

I know other teachers who also decided to blog about their AP CSP classes. I want to learn from you, so I am linking to those here.

Daniel Schneider normally blogs here and has an AP CSP blog here.

Matt Owen normally blogs here and has an AP CSP 180 blog here.

Kaitie O’Brian blogs about both AP CSP and AP CSA here

David Griswold blogs about AP CSP here

Steve Svetlik blogs about AP CSP here

Steph Reilly started a 180 blog for AP CSP here