Engaging students: Finding the area of a right triangle

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for engaging their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Ashlyn Farley. Her topic, from Geometry: finding the area of a right triangle.

Music is a large part of entertainment in today’s society, thus bringing in music to the classroom can help students relate to the material more. There have been studies that shows music activates both the left and right brain, which can maximize learning and improve memory. Along with the fact that it’s easier to memorize lyrics to a song than a fact, music-based learning can be engaging and impactful. It’s the same reason why musicians put a hook in their songs; brains look for patterns to better understand and process information. For the area of a triangle there are two examples, one is a rap by PBS, “Area of a Triangle Musically Interpreted,” the other is a pop parody, “Half It Baby.” By having multiple types of songs, students who have a variety of musical interest can each make a personally connection, and having a parody makes memorizing the lyrics even easier since the students will already have a reference of the melody in their brains. These songs, and other types, can be found on YouTube.

Origami is heavily based in geometry, so many lessons, such as finding area, can be created. One activity that could be engaging for the students, and have the students find the area of a triangle themselves, is with origami. The idea is that the students will create their own origami figures, after taking the area of the paper they are working with. After folding the shape, the students are to find the area of each shape, which should add up to be to total of the paper. Therefore, this project, applies the ideas of finding the area of a triangle, and finding the area of composite figures. Since origami is mainly quadrilaterals and triangles, the students are using what they know and see to figure out what the triangles’ areas equal. Because the students get to choose the origami figures, the material becomes personalized by their choices. However, this can be a difficult task if not scaffolded correctly, thus the teacher should take precautions. Done correctly, this project can be done as PBL if desired, not just group work.

Finding the area of a triangle, as well as many other shapes, is very important in architecture. However, architecture, and its designers, have very different understandings of the triangle’s meaning. A basis for all architecture, is the fact that triangles are common because the design and symmetry aid in distributing weight. Some examples of famous long-standing triangles in architecture are the Egyptian pyramids, The east Building in the National Gallery of Art in Washington, the Hearst Tower in Manhattan, the Louve in France, and the Flatiron Building in New York City. Some of these designs are using triangles as support, while others are used for decoration. However, according to Feng Shui, the triangle should be avoided, both in terms of architecture and interior design. The triangle is associated to fire energy which is chaotic energy. When triangles are used, they should point upward, implying the upward movement of energy. As seen, there are many times that the area of triangle is needed in architecture.

Resources:

Engaging students: Finding the area of regular polygons

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Conner Dunn. His topic, from Geometry: finding the area of regular polygons.

How can technology be used to effectively engage students with this topic? Note: It’s not enough to say “such-and-such is a great website”; you need to explain in some detail why it’s a great website.

A good way to get students into the concept and see it’s real life use is to be given a realistic problem. The natural world doesn’t typically give you perfectly regular polygons, but we certainly like making them ourselves. Better yet, we can make regular polygons of a certain area knowing the methodology behind computing their areas. Using GeoGebra, I can challenge students to construct a regular polygon of an exact area using what they know about the use of equilateral triangles to compute area.

For example, let’s say I ask for a hexagon with an area of 12√3 square units. While there’s a few strategies of constructing a regular hexagon that Geometry students may know of, the strategy to shoot for here is to recognize this means we want a hexagon with a side length of 2 then construct the triangles. GeoGebra allows for students to use line segments and give them certain lengths, as well as construct angles using a virtual compass tool. Below is the solution to this example by constructing 6 equilateral triangles (each with an area of 2√3 square units) to form the regular hexagon.

This image has an empty alt attribute; its file name is geogebra-hexagon.png

How does this topic extend what your students should have learned in previous courses?

By the end of the unit, students will have learned the formula for finding the area of a polygon (A = (1/2) * a * p, with a being the apothem, and p being the perimeter). But a big part of this unit is how we derive the formula from the process in which we solve the area using this equilateral triangle method. From many previous courses, students will have learned both the order of operations and properties of equality in equations, and we use this previous knowledge to connect a geometric understanding of area to an algebraic one. For example, when we have the idea of multiplying the area of an equilateral triangle by the number of sides, n, in the polygon, we have A = (1/2) b * h * n. It is by the use of communitive property that students can rearrange the variables like this: A = (1/2)h*b * n. And then we conclude that the b*n reveals that the perimeter of the polygon plays a role in our equation. This may seem subtle, but students being fluent in this knowledge helps them work in their geometric understandings much easier.

How has this topic appeared in high culture (art, classical music, theatre, etc.)?

A big part of the method for understanding area of polygons is seeing how we can perfectly fit equilateral triangles inside of our polygons of choice. Perfectly fitting shapes into and around other shapes is something you see in mosaic art everywhere, particularly in Islamic architecture.

While mosaic artists are not necessarily calculating the areas of their art pieces (they might but I doubt it), a big part what makes these buildings so nice to look at is how the shapes fit with one another so nicely. This is an art that’s very intentional in its aesthetically pleasing aroma. This is something I think Geometry students can take to heart when confronting Geometry problems (a just as well with future courses). It’s the overlooked skill of literally connecting pieces together in order to get something we want. In the case of the Islamic architect, what we want is a pleasing building to look at, but math, of course, brings in more possible things to shoot for and equips us with plenty of pieces to (literally) connect together.

Engaging students: Finding the area of a circle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Brendan Gunnoe. His topic, from Geometry: finding the area of a circle.

History: Squaring the circle

The ancient Greeks and other groups at the time had a fascination with geometry. These cultures tended to like thinking in terms of simpler geometric shapes, such as circles, equilateral triangles and squares. One of the classic problems proposed by these ancient peoples was “Can you create a square with the same area as a circle with finitely many steps only using a compass and straightedge?”. This problem stood for thousands of years, stumping even the most brilliant of mathematicians that attempted to show it true. Eventually, in the year 1882, it was finally proven impossible because of a property of the number π. It’s not too hard to show that π isn’t an integer, nor is it rational. What was left to show is whether π was algebraic or transcendental. The proof from 1882 showed that π is in fact transcendental, proving that it cannot be made using the rules set out by the original question. If a number is algebraic, then it is a solution to a polynomial with rational coefficients.

Curriculum: Using limit of triangular approximations to get the integral

The teacher starts off class by drawing a circle with an inscribed triangle, another with a square, and so on until a hexagon is inscribed. The teacher then draws isosceles triangles that originate at the circles center and extend to the corners of the polygons. The teacher could ask questions like “What do you notice about the total area of the triangles and the area of the circle as we keep adding sides to the polygon?” and “What do you notice about the triangles we made and the little wedges of the circle, what’s the same and what’s different about them?”. Then the teacher could arrange both the triangles and wedges in an alternating up and down fashion, almost like two zippers, to line up the triangles and wedges. The teacher could ask “What’s the length of the top of the triangles? What about the tops of the wedges, what’s their length?”.

Finally, the teacher asks “What happens when we let the number of pieces gets REALLY big? What happens to difference between the area of the triangles and wedges? What about the tops of the triangles and the tops of the wedges?”. In the limit, the upper edge converges to half of the circumference of the circle and the height of the triangles converges to the radius of the circle. Using this line of thinking, the teacher guides the students into seeing how you can derive the equation for the area of a circle by using approximating it with triangles, and then looking at what happens in the limit.

Application

A telescope’s lens is what’s used to control how much light gets into the eye piece. Suppose you’re an astronomer and want to take a photo of the full Moon on a clear night, which gives off 0.25 lumens/s-m². Suppose your camera needs to get a total of at least 3 lumens to produce a good photo and 5 lumens to get an amazing photo. What’s the radius of a lens (in centimeters) that can take a good photo in 10 minutes? What’s the radius of a lens that can take an amazing photo in 10 minutes?

Now suppose you’re working with the Hubble space telescope in low Earth orbit trying to get photos of a nearby star system. The radius of the main telescope is 120cm and the star system you want to observe is giving off light at a rate of 10^-5 lumens/s-m². How long will it take to get a good photo with Hubble? What about a great photo?

https://en.wikipedia.org/wiki/Hubble_Space_Telescope

https://en.wikipedia.org/wiki/Squaring_the_circle

Engaging students: Finding the area of a right triangle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Trenton Hicks. His topic, from Geometry: finding the area of a right triangle.

As an engagement activity, give students the following problem: “A rectangle has dimensions of base: b and height: h. How many different ways can you cut this rectangle in half with a straight line? How many shapes can you make from the different ways you cut the rectangle in half? Now out of those, which shapes are not rectangles?”

This will leave only two different ways to cut the rectangle in half, yielding identical triangles on either side of the line. Now, ask the students, “From what we’ve already learned about rectangles, what would be the area of this rectangle?” After confirming the area is base times height, wait a few moments before saying anything else. Now that the students are thinking about the base, they will now start to make predictions about the triangles that we’ve just made and their areas. Have them write their guesses for the formula of the triangle down on a piece of paper, and keep them to the side through the lesson. From here, we can break them up into groups and give them 3 right triangles to solve for the area, and one equilateral triangle to solve for the area. Go through the answers together and compare groups’ answers, as well as their predictions on what the area of a triangle is. The odds are, many groups will be stuck once they get to the equilateral triangle. If so, you may want to send them back to their groups to try and find the area, giving them the hint, that they may have to make new shapes, just as they did with our rectangle at the beginning. This lesson assumes that the students understand the pythagorean theorem so they can solve for the height of an equilateral triangle by making a new triangle. This way, the students can explore the phenomena of triangles’ area, and see if they can recognize that the height isn’t always a side of the triangle, but rather something they may have to solve for.

The students should be able to use similar techniques to find the area of a parallelogram, trapezoids, and other shapes, as these shapes are partially composed of triangles. As students progress to more complex 2-dimensional shapes, you can derive formulas as you go. As you move onto 3-dimensional shapes, we actually see lots of different triangles appear in the shapes’ respective nets. For instance, when computing the surface area of a triangular prism, we need to know how to compute the area of the base. We also see this same idea in computing volumes of triangular prisms, where we need to know the area of the triangular base. This is also applicable to pyramids, tetrahedrons, and octahedrons. Finally, these ideas are brought up again later in trigonometry where we can determine different parts of the formula with trigonometric ratios and functions and whenever the students learn Heron’s formula.

This concept of finding the area of a triangle expands many things that the students may already know. This won’t be the students’ first time seeing a triangle, nor will it be the first time they compute the area. Overall, this content should be a refresher and not new to the students. However, this may be the first time that the students are presented a rectangle and told to make a triangle out of it. From that point, they are told to make conclusions about the triangle’s area based on the rectangles area. As students think through this, they are using logic and reasoning to argue what makes geometric sense to one another. This further develops their mathematical reasoning skills, which may be a bit rusty since we far too often focus on the “what” and not the “why” and “how.”

Engaging students: Finding the area of a square or rectangle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Austin Stone. His topic, from Geometry: finding the area of a square or rectangle.

How could you as a teacher create an activity or project that involves your topic?

There are many applications to the real world that involves geometry and specifically area of squares and rectangles. Students could use this topic to find the cheapest cost of tiling the floor of a bathroom. Giving them the dimensions of the different tiles and the cost of each tile, students would have to find the area of the bathroom floor and then be able to pick the set of tiles that would be the most efficient and cheapest. This gives students a real world application to what they are learning while also giving them practice in finding the area given dimensions of a square and/or rectangle. This project also calls back to prior knowledge such as perimeter of rectangles and multiplying cost of one tile with the number of tiles used to get to total price. This project could also be a small part of a bigger PBL using area and perimeter of multiple polygons.

How does this topic extend what your students should have learned in previous courses?

The obvious prior knowledge to finding the area of a square of rectangle is being able multiply two numbers which is learned back in grade school. If the students are given the area of the square or rectangle and labeling the sides with a variable, the students would have to be able to solve for the variable. By doing this they would have to be able to multiply binomials (or polynomials if you want students to have more of a challenge). Once they multiply the two binomials and set the equation equal to the area given, they would then have to use the quadratic formula or factor which is learned in Algebra I. If students are given one side and the area, then they would have to solve for a variable with degree one which is used continually in all math classes. Depending on what information is given in the area problem, students will have to use prior knowledge to determine the answer.

How have different cultures throughout time used this topic in their society?

In East Asian mathematics during the 1^st-7^th centuries, a book called The Nine Chapters gives formulas for solid figures including squares and rectangles. The formulas are given as series of operations to get the result, called algorithms. Instead of variable and symbols, the formulas are given in sentences as in, “multiply the length of the rectangle by the width.” This puts the regular A=lw into words so that if someone who had no idea how to compute the area, they would be able to understand by the sentence given. This undoubtably was much more difficult to follow and became too long of descriptions for more complex figures, as this way of mathematics ended in Eastern Asian in the 7^th century. That does not mean that this way of math was not important. This put words into formulas instead of symbols which made it easier to understand for those that are learning it for the first time.

References

https://www.britannica.com/science/East-Asian-mathematics/The-great-early-period-1st-7th-centuries

Engaging students: Finding the area of a right triangle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Andrew Cory. His topic, from Geometry: finding the area of a right triangle.

How can this topic be used in your students’ future courses in mathematics or science?

Finding the area of a right triangle opens up the door to all sorts of applications in the future. The next step is the Pythagorean theorem which is used constantly throughout many math courses. The study of right triangles also opens up the world of trigonometry with students will be using in nearly every math course they go on to take. Once knowledge is learned of right triangles, other triangles can be manipulated to look like right triangles, or to create right triangles within normal triangles. Triangles are even utilized when determining things about other shapes as well, such as dividing rectangles into 2 triangles and other manipulations. If they go on to pursue geometry further, the Pythagorean theorem is one of the first couple of theorems proved and used in book 1 of Euclid.

What interesting things can you say about the people who contributed to the discovery and/or the development of this topic?

Pythagoras was a Greek philosopher that contributed to right triangles. He is credited with discovering possibly one of the most important right triangle properties. A legend says that after he discovered the Pythagorean theorem, he sacrificed an ox, or possibly an entire hecatomb, or 100 cattle, to the gods. The legitimacy of this legend is questioned because there is a widely held belief that he was against blood sacrifices. The Pythagorean theorem was known and used by Babylonians and Indians centuries before Pythagoras, but it is believed he was the first to introduce it to the Greeks. Some suggest that he was also the first to introduce a mathematical proof, however, some say this is implausible since he was never credited with proving any theorem in antiquity.

How can technology be used to effectively engage students with this topic?

Applications such as Geogebra can be used for any type of geometry activity. It is a great way to help kids visualize what is happening with shapes in geometry, something that is usually a struggle for students. For helping students understand how to find the area of a right triangle, it can easily be shown that if you take a rectangle, or a square, and cut it in half diagonally, you get two right triangles. And since the area of a right triangle is half of the area of a rectangle or square. The various ways that shapes can be manipulated virtually can be a big help for students that learn in different ways. Being able to view shapes in different ways opens doors for students who traditionally struggle seeing a shape in their head, and using it to solve their problems.

Sources

https://en.wikipedia.org/wiki/Pythagoras#In_mathematics

Facts about the 6-foot zone

Source: https://xkcd.com/2286/

Engaging students: Area of a trapezoid

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Lissette Molina. Her topic, from Geometry: finding the area of a trapezoid.

How could you as a teacher create an activity or project that involves your topic?

I believe most students in America all discovered finding the area of a trapezoid with one very easy and simple activity. Students are to receive a trapezoid of some different sizes. They are then asked to find area by cutting off the triangular sides. The student then finds that all trapezoids are composed of triangles and a rectangle. This is a very quick activity that requires students to come up with a formula that works across all trapezoids. Learning about finding the area of a shape with hands-on discoveries keeps the formula and how it became embedded into students’ memories. This activity may also work with most polygons.

How does this topic extend what your students should have learned in previous courses?

Find the area of a trapezoid does not require much information from previous courses. One major topic the student should be able to have learned before coming into a geometry class should be area. However, very rarely, students do not know what area is already. So, the student should be able to apply what they know about area into finding the area of a trapezoid. This involves finding the area of a rectangle and a triangle. It is important that a student understands exactly where a formula is derived, so it is also important that students know that the trapezoid contains two shapes and that finding the area of those two shapes will help them find the area of the resultant trapezoid.

How can technology (YouTube, Khan Academy [khanacademy.org], Vi Hart, Geometers Sketchpad, graphing calculators, etc.) be used to effectively engage students with this topic?

One helpful website or program is Desmos (desmos.com). There are usually modules made for students often made by teachers. I have not yet come across one already made, but here is what I have in mind. Desmos is primarily made for graphing, but there are so many functions in this website that it can be manipulated to perform other things such as the unit circle. One very helpful idea would be to make a shape of a trapezoid by combining two triangles of different sizes off each of a rectangle’s sides. Since these shapes are placed on top of a graph, students would be able to calculate the area by counting the square units. WIth triangles, students can count the number of half, quarter, etc. square units. This way, students can find the area of a trapezoid by counting the squares, and realize that it would be easiest to find the area of those two triangles and one rectangle and combine them.

Engaging students: Finding the area of a square or rectangle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Christian Oropeza. His topic, from Geometry: finding the area of a square or rectangle.

How can this topic be used in your students’ future courses in mathematics or science?

Finding the area of a square or rectangle comes up again later in Geometry when solving for the surface area of a prism. The reason behind this is because any n-sided prism, where n is the number of sides the base of the prism has, will have n many squares or rectangles. Therefore, in order to calculate the surface area of any prism, the use of finding the area of a square or rectangle is required (Reference 1). Another course that involves this topic is Calculus. When approximating the area under a curve, one strategy is to use left or right endpoint approximation which is just the sum of the areas of the rectangles under or over the curve (Reference 2). This topic is also used in physics when covering measurements. The idea of finding the area of a square or rectangle in the measurements section is to precisely and accurately find the area.

How has this topic appeared in the news?

Steiner Ranch is a hair studio that just recently added 1600 square feet, thus bringing their total to 3468 square feet. With the addition of more space the studio now holds: 19 stylist chairs, 8 shampoo bowls, 3 restrooms, and a color mixing room. All in all, this could not have been done without the use of finding the area of a square or rectangle because then the owner, Brian Charles, would not know how much of each studio equipment would be able to fit in a way that was fitting for him (Reference 3). In other news, state deputies of the Legislative Assembly of Rondonia decided to try creating 11 new protected area in the Brazilian Amazon, which amounted to a total of 2,316 square miles. Therefore, the use of the area of a square was used to determine how much area would go to the new protected areas. However, the bacanda ruralista agribusiness lobby opposed this decision and passed a bill that did not allow the process of making the protected areas (Reference 4).

How have different cultures throughout time used this topic in their society?

During 570-495 BC, the use of finding the area of a square impacted math in Greek culture. More specifically, a man by the name of Pythagoras created what is known now to be the Pythagorean Theorem. He discovered this theorem by noticing that the area of the square created by the hypotenuse of a right triangle is equal to the sum of the area of the squares created by the other two sides of the same right triangle (Reference 5). Also, there were different cultures who had discovered the same formula as the Pythagorean Theorem, but were not the first to publish their findings. These different cultures include: Mesopotamian, Indian, and Chinese (Reference 6). Finding the area of a square or a rectangle comes up immensely in computing the cost for installation of hardwood floors. The cost is computed by charging the customer for the price of each square foot of wood used and the labor for each square foot of wood installed (Reference 7).

References:

Engaging students: Finding the area of a square or rectangle

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Trent Pope. His topic, from Geometry: finding the area of a square or rectangle.

How could you as a teacher create an activity or project that involves your topic?

On this website I saw that the Kelso High School GIC students went out and built a home as a class project. They were able to get a $13,000 grant from Lowe’s Home Improvement and blueprints from Fleetwood Homes to go out and build a physical house. I like the idea of having students use geometry in a real world application, as a teacher I would bring this idea to paper. Students would design and create blueprints for their dream house using squares and rectangles. I would start by giving them the total area their house will be. For example, I would tell them to make the blueprints for a 400 square foot house. They could have anywhere from 5 rooms to 20 rooms in their house. They will be responsible for showing the measurements for each room. After creating the layout of the house and calculating the areas of each room, students will be given a set amount of money to spend on flooring. They will then calculate the cost to put either carpet, wood, or tile in each room. This is to have students decide if they would have enough money to have a large room and if so what flooring would be best. There are other aspects you can add to this project to make it more personalized, but as teachers we just want to make sure we are having students find the area of square and rectangles.

http://tdn.com/news/local/geometry-in-construction-class-finishes-building-first-home/article_74143492-d7a9-11e2-995a-001a4bcf887a.html

How has this topic appeared in the news?

There are many instances of where area made the news. I found multiple websites that talk about how schools are having building projects for geometry and construction classes. These students are building homes from 128 square feet to 400 square feet. Teachers are having students make these homes so that they can see that geometry is in the real world. By having a range of sizes, students have to adjust their calculations. When creating a house or mobile home you need to accommodate for walking space in each room. In order for students to know if there is enough space, they must find the area of each room. Teachers are using this project because blueprints for houses only use squares and rectangles, making it easier for students to practice solving for area of these shapes. This is just the start of teachers making the concept of area more applicable.

http://design.northwestern.edu/projects/profiles/tiny-house.html

How have different cultures throughout time used this topic in their society?

The topic of finding area of squares and rectangles is used throughout many cultures. In the Native American culture along with todays, we see it in growing crops. A farmer must know how big their crop is so they can figure out how much food they will have at harvest. An instance used by many cultures is creating monuments in the shape of square pyramids. In order to build it the right way, you must know the area of the bottom base to build on top of that. A final use of it in our culture is in construction, when we decide how we want to build a building. The concept of area is something that many cultures use today because of how easy it is to calculate. This creates a great way for cultures that are less educated to become familiar with the same concepts as other cultures.

References

Geometry in Construction class finishes building first home. n.d. <http://tdn.com/news/local/geometry-in-construction-class-finishes-building-first-home/article_74143492-d7a9-11e2-995a-001a4bcf887a.html>.
Tiny House Project. n.d. 6 10 2017. <http://design.northwestern.edu/projects/profiles/tiny-house.html>.