Illustrative Mathematics
Similar Triangles
Proving triangles are similar is often an exercise in applying one of the many theorems young geometers memorize, like the AA similarity criteria. But proving that the criteria themselves are valid from basic principles is a great...
National Security Agency
Classifying Triangles
Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy Triangle,...
Alabama Learning Exchange
Triangle Area: No Height? Use the Sine
No height? No problem! Learners use their knowledge and a little help from GeoGebra to develop the Law of Sines formula. The Law of Sines helps to determine the height of triangles to calculate the area.
CPALMS
2D Rotations of Triangles
Where does the line of rotation need to be to get a cone? Pupils respond to three questions involving rotating a right triangle about different lines. The scholars describe the solid created along with providing details about its...
Curated OER
Exploring Centers of a Triangle: Part 2
Students model and solve a real-world problem by constructing the centroid of a triangle. They explore relationships of the medians of a triangle and investigate how the centroid partitions each of the medians. Students investigate...
Curated OER
Triangle Inequality Theorems Investigation
Students estimate and measure triangles. In this geometry lesson, students identify the relationship between three sides and a triangle. They use the inequality theorem to decide if a triangle will be formed or not.
Curated OER
30-60-90 Right Triangles in Cabri Jr.
Young mathematicians draw and label right triangles using Cabri Jr. technology. They create other special right triangles and identify the length of the hypotenuse and each leg. Students explore the ratios to determine how the hypotenuse...
EngageNY
Modeling Riverbeds with Polynomials (part 2)
Examine the power of technology while modeling with polynomial functions. Using the website wolfram alpha, learners develop a polynomial function to model the shape of a riverbed. Ultimately, they determine the flow rate through the river.
Curated OER
Exploring Characteristics of Triangles
Young scholars draw triangles and explore the classification of each using the measures of interior angles and lengths of sides. They investigate the sum of the interior angles of various triangles and conjecture and prove the theorem:...
Curated OER
Triangles & Congruence, Proportions & Similarity, Right Triangle & Trigonometry
Young scholars are introduced to the topic of congruence and proportions in Geometry. Using technology, they construct and validate the properties of various geometric figures and identify whether it is congruent or proportion to the...
Noyce Foundation
Parallelogram
Parallelograms are pairs of triangles all the way around. Pupils measure to determine the area and perimeter of a parallelogram. They then find the area of the tirangles formed by drawing a diagonal of the parallelogram and compare their...
Inside Mathematics
Hopewell Geometry
The Hopewell people of the central Ohio Valley used right triangles in the construction of earthworks. Pupils use the Pythagorean Theorem to determine missing dimensions of right triangles used by the Hopewell people. The assessment task...
Inside Mathematics
Rhombuses
Just what does it take to show two rhombuses are similar? The assessment task asks pupils to develop an argument to show that given quadrilaterals are rhombuses. Class members also use their knowledge of similar triangles to show two...
Curated OER
What are the Kinds of Triangles?
Fifth graders classify triangles. In this triangle lesson, 5th graders learn about the characteristics that make up a triangle. They are instructed through video, PowerPoint slides, and teacher-led demonstrations.
Curated OER
Triangle Inequality Theorem
High schoolers investigate the relationship between angle measures and sides of a triangle and the relationships among the three sides of a triangle. The use of technology (Cabri, Jr.) allows learners to make and test conjectures as they...
Curated OER
How many isosceles triangles can you find?
Seventh graders recognize the characteristics of isosceles triangles. In this isosceles triangle lesson, 7th graders use geoboards to create isosceles triangles. Students record results and explain why they have an isosceles triangle.
Curated OER
Exploring Geometric Figures
Tenth graders explore mathematics by participating in hands-on daily activities. Learners identify a list of different shapes and classify them by shape, size, sides and vertices. They utilize tangrams and geometric pieces to gain an...
Curated OER
Similar and Congruent Triangles
Students create and classify different types of triangles using an online geo-board. They explore the concepts of similar and congruent as they discover how to draw similar and congruent triangles.
Curated OER
Finding Remainders in Pascal's Triangle
Students use clock arithmetic to find remainders. In this patterns in math instructional activity, students explore the relationship between clock arithmetic and remainders using a computer applet. Students also identify patterns in...
Inside Mathematics
Rugs
The class braids irrational numbers, Pythagoras, and perimeter together. The mini-assessment requires scholars to use irrational numbers and the Pythagorean Theorem to find perimeters of rugs. The rugs are rectangular, triangular,...
Texas Instruments
Getting Started with Cabri Jr.
Pupils construct geometric figures using Cabri Jr. in this constructing geometric figures using Cabri Jr. instructional activity. They familiarize themselves with Cabri Jr. and construct segments and triangles. Your learners will use...
Curated OER
Constructions of Isosceles and Equilateral Triangles
Pupils explore the difference between drawing and constructing a triangle utilizing The Geometer's Sketchpad on the computer. They create, develop and script constructions for both isosceles and equilateral triangles. Each student has to...
Curated OER
Special Right Triangles
Students identify different types of special right triangles. In this geometry lesson, students differentiate between right triangles and isosceles triangles. they construct the triangles using geometry software and make conjectures...
Curated OER
Triangle Exploration
Students are introduced to The Geometer's Sketchpad software while in the computer lab. They focus on triangles, horizontal lines, vertex and top parallel lines. Each student utilizes geometry to complete basic geometric constructions.