1-Var Page 1: Entering Data and Calculating Statistics

]]>At the same time, the math involved in the perimeter of polygons is pretty simple: its the sum of the lengths of the sides. There’s a reason it’s introduced at third grade (in the Oklahoma standards, at least.) But while adding a set of numbers is pretty easy for a high school student, I wanted to layer in more challenge.

My students need to figure out the missing side lengths of the polygon before they can make that simple calculation. Or, they’ll get the perimeter and have to figure out something else. Given this unit has already covered theorems related to quadrilaterals, and the previous unit was on the Pythagorean theorem, special right triangles and trigonometry, I had lots of options of for how to make students determine the information they need.

Also, students complain all the time about word problems, which tells me they probably need more exposure to and practice with word problems. So I gave my students ten problems, for which they had to draw a diagram (as I hadn’t given them one) and show all their mathematical working.

]]>These seem simple, but there are subtleties to understanding what area really is, which I’ve even seen calculus students mess up with. If you ask students what area is, they often respond with something like “area is the inside, and perimeter is the outside,” but then can’t elaborate on that. The common confusion between concepts of length and area is demonstrated by students frequently stating the area of a shape in length units.

This is why I like using the cutting and pasting of paper to represent area. I find students can conceptualize the amount of paper used to make a shape much easier than the abstract idea of “area”, even though they are fundamentally the same thing. Students can understand that one shape has more area than another using the fact that it took more paper to make. Also, if you can demonstrate that two shapes can be constructed from the exact same amount of paper, students can understand that they have equivalent areas.

This activity uses the area of a rectangle to find the areas of other polygons. Students are given a page with templates for the shapes they’re going to create, and a colored half sheet of rectangles and octagons. (The colored half sheet is actually double the number of shapes they need, but it makes things easier to have spares if they make mistakes.)

Everyone also needs a glue stick, a pair of scissors, a ruler and a pencil.

The white sheet can be cut into the six separate sections. On the back of each section, there are instructions on how to construct the given shape from a rectangle.

Students should follow the instructions to construct each shape from one of the small colored rectangles. Reactions will range from “this is easy”, to “I think I’ve got it, can I check what you did”, to “this is impossible!” Make sure you’re cycling around the room a lot, because students can and will fall behind quickly if they’re not paying attention. Frustratingly, I found most of the students who thought the instructions didn’t make sense hadn’t actually taken the time to read them step-by-step.

I suggest doing them in the order of rectangle, parallelogram, triangle, trapezoid, kite and polygon. Once they’re done, they’ll look something like this:

The idea is that each shape has an area equivalent to a rectangle in some way, because they used the same amount of paper. The triangle and the kite are related by a half, because one rectangle was able to make two of these shapes. The regular polygon is a little different, as it starts with the polygon and is deconstructed into half a rectangle; we know it’s half, as we already showed that triangles make the area a half. Add some labels to the shapes, and you get something like this:

In the trapezoid, “m” is referring to the midsegment (or median) of the trapezoid. We’ve already covered the the theorem that says the midsegment length is the mean of the base length, which is why we’re able to substitute (b_{1} + b_{2})/2 for m without any further working.

If you’d like to do this, files can be downloaded here. Included are alternate versions for non-Americans who think “trapezoid” is a weird word. Font is Matiz.

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To be clear, this is not supposed to be a textbook. The way I see it, most math textbooks aim to do three things:

- Explain mathematical concepts.
- Give “worked examples” explaining how to do different types of questions.
- Provide a bank of practice questions.

“Explaining mathematical concepts” would be better described as “guiding students to a conceptual understanding of mathematics.” That’s not something a textbook can do because *the textbook doesn’t know the students its guiding*. I believe students are best served when they construct their knowledge of math themselves, under the guidance of their teacher.

And the “worked examples” should be the job of the students, again, with guidance from the teacher. Those examples should be developed either by individual students, groups or the whole class as appropriate, with the teacher checking to make sure mistakes aren’t showing up along the way. Many of the examples in my classes end up following a slightly different path than I’d have followed, because it made the most sense to the students at the time. But a textbook’s examples are fixed, and don’t allow students to think of how they’d solve problems themselves.

That leaves us with the practice questions. This has been, in the past, how I’ve seen textbooks as being the most useful. But the textbooks I teach with (or more correctly, don’t teach with as they sit in the cabinet) don’t do a great job of that either. They are seriously outdated, and while they make some token effort of demonstrating their alignment with Oklahoma’s standards, they’re the old PASS standards, not the Oklahoma Academic Standards we’ve had for over a year now. And most of the time, it’s hard to find questions I can use, because the sequencing of the book is nothing like that of my class (probably because my sequence was developed by myself from the standards the book is not aligned to.)

That has left me looking to other resources (typically online) to find practice questions in. But that’s often frustrating too, and can sometimes result in spending hours searching for the type of practice assignment that I feel should exist, somewhere, but I just can’t find. Sometimes I find questions that assume knowledge my students don’t have yet, or assume my students don’t know something they do and don’t go deep enough. Or they prescribe a particular method to solve a question; there’s nothing more frustrating than a good assignment ruined by “use FOIL to.” Then, with my preparation time wasted, I have to create my own questions anyway.

I’ve often said, “Someone should write a book of practice problems for Algebra 2. Sort of like a textbook, but without the explanations and examples I can provide myself.” And somewhere along the way, “someone should” became “I should.”

To date, I’ve been following these objectives when writing this book:

- All work should align to the Oklahoma Academic Standards, which I’ve mostly done by ensuring my existing units and skills align to the standards, though some questions may exceed the standards.
- Avoid telling students how to solve a problem. I do break this rule sometimes (for instance, there’s a question where students are told to use completing the square, even though it isn’t needed, because practicing completing the square was the point of the question.)
- Provide scaffolding through the sequencing of questions, rather than giving students too many instructions.
- Where possible, provide some backwards, “Jeopardy”-style questions. As in, the solution was …., what was a possible equation?
- Where possible, provide “Further Practice” sections, suggesting to students how they can create their own questions (often with a partner) if they’re looking for, well, further practice.
- Look as professional as possible. I’ve learned a lot about LaTeX recently…
- All questions are originally my own. I own the copyright, so that I can use it how I like.
- I’m sure there were others, but it’s late and I really need to get to bed…

Working title is “Mr. Carter’s Algebra 2 Practice Book.” But I don’t want it to just be mine, I want other teachers to make use of it as well. To that end, I’m planning to make various draft versions available to download even at this *very* early stage.

**Mr. Carter’s Algebra 2 Practice Book
Version 0.1.0 (January 14, 2018)**

Please, have a look through it, use it in your classroom if you’d like. I’d like suggestions, though please don’t be too harsh. As I’ve said, even these chapters I’m sharing are in a very early state. I’m actually feeling nervous about sharing this, as a lot of work has gone into it, but there’s a lot more work to do. But I’m taking a risk here, because I believe this project can do what my blog also aims to do: to make me a better teacher, and possibly help other teachers out along the way.

]]>To start with, I posted this data in Desmos on my smart board:

There’s nothing special about the data, they were just the numbers I happened to type into Desmos at the time. If I was going to do this again in the future, I think I’d want to source some real-world data to use. But as this activity didn’t have a whole lot of preparation go into it, there wasn’t a whole lot of opportunity to find that data. (That said, if you’d like to use my artificially created data, go for it.)

I had students create their own scatter plots for the data. Once they had done this, I told them to rule a line through the data that they thought summarized and modeled the data as well as possible. I informed them that there is an objective way to determine which equation does the best job of this, so it was now a competition.

Then the moment that revealed to us just how rusty some of their algebra skills are: I had them each find the equation of their line. After they complained that it’s been too long since Algebra 1 (despite most of them seeing this in Algebra 2 or Geometry with me last year), and a quick recap tutorial on slope-intercept form, they were able to find their equations.

Then to compare them, I typed their equations into Desmos so that we could visually compare them. I’m happy to say that most of the equations fit the data reasonably well, at least to the naked eye (which is, of course, all my students had to work with for the activity.) Then, I added one more line: the regression equation created by Desmos itself (in orange.)

One of the lines (the blue dashed one) is actually very close! I also changed all of my students’ equations into regression equations, so we could compare their R^{2} values. For now, I just told them that this is a measure of how well the model fits the data. In future lessons, I will explain the more formal meaning to them.

To finish our discussion, I had Desmos plot the residuals for the linear regression equation, as well as for some of the students’ equations. I explained that what Desmos was doing was trying to make these residuals as close to zero as possible. Over the next few days, we’ll start to get into the details of how the mechanisms of regression actually work. But for this lesson, I wanted to give students a sense of what regression is about, rather than how it works.

]]>Each group contains four cards: the name of the quadrilateral, a diagram, the definition, and a list of the other shapes quadrilateral is an example of. The diagram shows only the information that’s stated in the definition. Other properties of the quadrilaterals are covered in the following skills (some of which I’ve already blogged about.)

]]>While they were doing that, I passed out a set of four Exploragons to each student, with two each of two different colors/lengths. I also made sure that each pair of students received the same colors, which will be important later.

If you haven’t used Exploragons before, they’re plastic sticks with little nubs that allow the sticks to snap together to make different geometric arrangements. Other companies sell them as AngLegs, though I think prefer Exploragons as they have nubs in the middle of the sticks, not just at the ends. When I started teaching at Drumright, I had the opportunity to order hands-on supplies to use. I’ve found that of everything I’ve ordered, these are the most versatile physical tool I have for teaching Geometry.

I gave students the instruction to construct a parallelogram from the pieces I gave them. Thankfully, they (mostly) ended up with something like these:

I then instructed them to write down everything they noticed about their shapes, and to discuss what they notice with the students around them. Answers ranged from what I was hoping they’d notice (opposite angles are the same, opposite sides are the same length) to not as useful (“it’s a shape”), but getting the perfect answer wasn’t really the point. I wanted students to understand that there are things about these quadrilaterals we can know are true aside from just their definitions.

Next, I told students to do the same thing by making a rhombus. Thankfully, they realized I didn’t have the right pieces to do this A few looked at me incredulously, a few demanded I give them more pieces (which I refused), but slowly a few students worked out what they needed to do: trade pieces with the person next to them.

Once students had had time to write down their observations of their rhombus, we started our notes summarizing the theorems for these quadrilaterals. I used the observations as a springboard into this conversation, pointing out that some of the theorems matched what they’d noticed, and some didn’t (particularly the ones involving diagonals.)

After, students started the activity I put inside the notes. For each diagram they needed to identify four things:

- What the shape is (admittedly not too difficult, as there’s only two to choose from.)
- How they know it’s that shape, based on either one of the theorems or the definition of the shape.
- The value of any variables in the diagram.
- How they know it’s that value, again by referencing a theorem or definition.

There is a flaw in these questions. All of the parallelograms have a horizontal pair of sides, while the rhombuses are in a “diamond” position. This made distinguishing the two a little too easy. If I get a chance, I’d like to rotate some of the diagrams to different angles.

Downloads for these notes can be found here.

]]>To help focus on the fundamental properties of each function, we used the following template each time we introduced a new function.

Importantly, I had the students figure out details as a class. After stating the rule for the function, we always filled in the two-sided number line, with inputs on the top and outputs on the bottom. I chose to use a number line instead of a table, as it allows me to point out the continuous nature of the values between each mark on the line.

Then we filled in the domain and range, examining the inputs and outputs to determine these. We also determined if the function is one-to-one or many-to-one. I’m really proud of how my students have become increasingly confident in determining these answers for themselves from their own understanding of the functions and their values.

Next, we plotted the function on the grid. The number line is deliberately aligned with this grid to help students make the connection between the two. I have a SmartBoard template set up with points along the x-axis, with which we move points up or down to plot the function, to emphasize how the graph demonstrates the connection between input and output values. Then knowing the shape of the graph allowed us to easily fill in the rest of the table.

The inverse function section depended on which function we were talking. Sometimes we filled it in immediately, as most students understood x² and √x as inverses. Other times we waited to fill it in, such as with exponential functions which was completed before we talked about logarithms.

The second part of this template are the two “Graphing Example” section inside.

In the past, I’ve found students resistant to showing all the algebra they needed when they sketch a graph (usually because all they wanted to do was copy what their calculator showed.) I wouldn’t say this template has completely changed that, but it has made a big difference. Students complained a bit at the start of the year, but they’ve learned to appreciate the guidance this provides and gained a lot of confidence in their graphing ability. I know students probably don’t need to find the transformations of the parent function for every graph they sketch, but I think having them do this for each question we practice has helped their understanding of why each function produces the graph it does, and has helped serve as a check for the other parts of the template.

We’ve often had to leave the x-intercept section blank, because we’ve started graphing each type of function before we looked at solving equations involving that function. This has actually worked out pretty well. I found students accept my explanation that “We can’t do this yet because I haven’t taught you how.” Then, when we come solving those equations (typically the very next skill), I can use the need to find x-intercepts as a motivation for practicing solving equations. Then we go back to our graphing examples, find the x-intercepts, and add that detail to the graph. My students are sometimes annoyed that we jump backwards in our notes sometimes, but I think they appreciate that I’ve tried to avoid overwhelming them with too many details they don’t need to see all at once.

That’s been my approach all of this year: the idea that students don’t need to see all the detail until they’re ready for it. For instance, while we’ve talked about quadratic functions, we’ve only dealt with the vertex form, as that’s the form that can be explained through transformations, fitting the function pattern we’ve been following. Yes, we still need to talk about factoring, distributing and all that fun stuff. But now I feel we have a structure to build everything else on. I’m actually looking forward to completing the square this year, as I have a really useful motivation for it: it allows us to put quadratic functions into the form my students are already very familiar with.

We’ve introduced our last parent function now, so I’m not going to get any more use out this template this year. To be honest, I felt a little sad when we finished our last one, because it’s worked so well this year. Also, it means I’ll actually have to produce notes for each lesson now, instead of using the same ones over and over again…

You can find PDF and Publisher files here.

Included is a second version that leaves out the parent function template for a third graphing example.

Below you can find all the parent functions from my notebook for this year, as well as a couple of the graphing examples pages.

**Linear Function**

**Absolute Value Function**

**Quadratic Function**

**Square Root Function**

**Cubic Function**

**Cube Root Function**

**Rational Functions**

**Exponential Function**

**Logarithmic Function**

**Graphing Examples**

This year, the start of the [Algebra 2] course is going to

focus on functions, transformations and inverses. For quadratics that means only dealing with vertex form, as well as showing the relationship to square roots. We’ll cover all the functions that way, before coming back to all the other algebra we missed along the way. So we’ll cover quadratics again, including all the factoring and solving stuff.

With that in mind, I thought I’d better make sure my students understand what a function is.

This is the front, basically just explaining what a function is. The examples on the bottom section were actually done after the notes inside. You could really use any examples you wanted. I chose these ones because this first unit focuses on absolute value functions, and I figured they should at least be able to evaluate quadratics, even if they don’t know anything else about them yet.

This is the part I’m most proud of. I think it lets students see clearly what the difference relation types are. I know it’s traditional to talk about the vertical and horizontal tests in this situation (and I did mention them briefly), but I decided to go back to the basic definitions of one-to-one, etc. and let students develop an understanding from those definitions. I was glad that by the time we did the last few diagrams, students were suggesting what the diagrams should be without any prompting.

Though they sometimes have to be prompted with “does each output have exactly one input,” most students have been good at recognizing the difference between one-to-one and many-to-one, which is critical as inverses are coming up soon. They often get many-to-one and one-to-many mixed up. They know which is which, they just get the names confused. I had a student say at one point, “So, it’s the number it goes from to the number it goes to, right?” Then after realizing what she’d just said, added “Oh, I guess that makes sense.” So, at least one of them has made that connection!

I know that it’s typical to make a mistake as a teacher and just claim it was to “see if you’re paying attention,” but in this case, having to cross out the bit that said “function” for one-to-many and many-to-many really was deliberate. (I promise I’m not just saying that!) Making students have to edit the page like this was an attempt to drive the point home that these are not functions. Thankfully, some of my students did notice that these sections contradicted the notes on the front of the foldable, and suggested it needed changing before I did.

]]>At this point, we’re *almost* ready to start talking about functions, but I wanted to “review” a few things about solving equations first. Which brings us to these pages.

Except, lets just pause for a moment, and examine those quotation marks around “review”. The linear equation stuff is straight-up review, but solving absolute value equations is one of those used-to-be-in-2-but-now-in-1 topics I wrote about last time. Which means it’s new to my students this year, but should be something my future Algebra 2 students have already seen. With that out of the way…

Nothing terribly complicated here. These *should* be equations my students know how to solve, but as I suspected would be the case, they needed some help shaking some of the cobwebs loose first.

I find students get a lot more frightened of linear equations than they need to be, especially when fractions start showing up. This was a good chance to have them use a strategy that shows up again and again in algebra:

If you don’t know how to solve this problem, turn it into one you can solve.

And that’s the principle behind the design of these notes. Each situation shown really only requires one or two steps to turn it into an equation like the one above.

I would never suggest teaching this stuff for the first time like this. There needs to be much more time spent developing understanding at each stage. But for review, I think it worked fine.

I very purposely didn’t use “cross-multiplying” as the final strategy. Those words are banned in my classroom. While it could solve the example shown, cross-multiplying is useless for any problem involving more than two fractions, for instance. Every so often, I have a student suggest cross-multiplying as a way to solve a problem. Never have any of them been able to apply it the way they were supposed to. So, I’d rather my students take one more step to solve an equation and actually understand what is happening, rather than totally confuse themselves.

Absolute value equations are not in the Algebra 2 standards, but I wanted to include them anyway, because:

- These students missed them in Algebra 1. (Which means I’m supposed to cover them anyway.)
- AFAIK they’re on the ACT. They’d be some pretty easy points my kids would be throwing away if they didn’t know this.
- I’m about to use absolute value functions as an example for transformations and graphing, to set up everything we’re going to do with other functions. It’s probably a good idea if they knew how to find some x-intercepts, then.
- I think it’s going to be useful to expose students to equations that can have two, one or no solutions. I heard a rumor that there’re these things called quadratics that do something similar…
- I also wanted kids to practice finding extraneous solutions, because that’s going to come up soon, too.

Notice that the notes don’t point out that the absolute value function cannot equal a negative number. That was there originally, but I took it out, and let students solve a few equations first before we talked about it. I was hoping they’d realize themselves, but it did take a little bit of prompting for them to realize that something like |x – 2| = -3 has no solution without having to go through all the steps. In any case, it show the value of checking the solutions of an equation.

In case you were wondering, it is possible to get an absolute value equation that has one legitimate solution and one extraneous solution. Try something like |x – 2| = 2x.

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