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...
Shodor Education Foundation
Triangle Area
While the instructional activity focuses on right triangles, this activity offers a great way to practice the area of all triangles through an interactive webpage. The activity begins with the class taking a square paper and cutting in...
Digging Into Math
Classifying Triangles
Young mathematicians explore the world of three-sided shapes in this lesson on the different types of triangles. Starting with a general introduction to classification using Venn diagrams, children learn how to categorize triangles...
Texas Instruments
Identifying a Triangle by its Sides and Angles
Identify triangles by their angle measures and side lengths by looking at and measuring angle measures and side lengths. Use Cabri Jr. to construct various triangles, then manipulate the construction to create the 6 types of triangles,...
Curated OER
Classifying Triangles by the Length of the Sides Using Cabri Jr.
Learners follow detailed directions to create triangles on their graphing calculator. In this properties of triangles lesson plan, they will create triangles on their calculators using the Cabri Jr. application. They then identify three...
Willow Tree
Three-Dimensional Figures
Time to move into the third dimension! Learn the names of the geometric solids and count faces, edges, and vertices. Then learn to recognize nets that create a given solid.
Willow Tree
Surface Area of Three-Dimensional Figures
Lateral area and surface area are simple concepts, but calculating them is not as easy! Using formulas, learners calculate lateral area and surface area for the same three-dimensional figures. The resource discusses the formula variables...
Curated OER
Geometric Figures-Triangles
Fourth graders explore triangles. In this math instructional activity, 4th graders discuss the different types of triangles. Students create triangles using wiki sticks. Students complete an online matching game.
Illustrative Mathematics
Lines of Symmetry for Triangles
What can symmetry tell us about triangles? After looking at four examples, learners will come to realize that lines of symmetry are different for equilateral, isosceles, and scalene triangles. Use this guided practice activity as an...
EngageNY
Putting the Law of Cosines and the Law of Sines to Use
Use the Law of Cosines and the Law of Sines to solve problems using the sums of vectors. Pupils work on several different types of real-world problems that can be modeled using triangles with three known measurements. In the process,...
Curated OER
SuperShapes, Part 1; "Tri"ing Triangles
An outstanding lesson on triangles awaits your math scholars. Learners focus on the triangle, which is the strongest of all polygons. They see the role that triangles play in the design of buildings, and learn about triangle...
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
Drawing a Triangle with Cabri Junior
Learners draw triangles on their graphing calculators using the Cabri Junior application. In this graphing calculator lesson, students follow step by step directions to create triangles on their calculator. They identify the type of...
Curated OER
Draw 3 Dimensional Objects
Bring three-dimensional shapes to life in your classroom. First introduce the vocabulary of three-dimensional shapes, such as sphere, cube, and pyramid. Then, show your kids examples of how to use two-dimensional objects draw...
Curated OER
Types of Triangles
Students classify triangles by the length of their sides. In this geometry lesson plan, students use a white board to demonstrate the angles of various triangles. Students construct an equilateral, isosceles, and a scalene triangle.
EngageNY
The Definition of Sine, Cosine, and Tangent
Introduce your classes to a new world of mathematics. Pupils learn to call trigonometric ratios by their given names: sine, cosine, and tangent. They find ratios and use known ratios to discover missing sides of similar...
Curated OER
Exterior and Interior Angles of Triangles
Tenth graders explore the exterior and interior angles of triangles. They use a theorem in order to prove a theorem about all polygons. Students use the theorem and its applications to find the angles of different types of triangles.
Centers for Disease Control and Prevention
Understanding the Epidemiologic Triangle through Infectious Disease
Introduce infectious diseases and the epidemiologic triangle. A helpful resource describes the agent, host, and environment from the three vertices as well as the time factor, which is in the middle. Scholars complete a simple...
Curated OER
Scalene Triangles
Fifth graders identify and classify scalene, equilateral, and isosceles triangles. In this triangle lesson, 5th graders define the different attributes of 3 types of triangles and sort them by descriptions and...
Curated OER
Travel Triangles
Learners demonstrate and understanding of the three types of angles using triangles and quadrilaterals. In this angles lesson plan, students learn about acute, obtuse and right angles. They use cut-outs to find the areas of triangles and...
Curated OER
2-D polygons
A hands-on activity uses the Zome modeling system, and helps young geometers either learn or review their knowledge of polygons. Students build as many different 2-dimensional polygons as possible: triangle, square, rectangle, pentagon,...
Curated OER
Triangle Congruence with Coordinate
Two triangles are displayed on a coordinate plane. Youngsters apply a reflection and a translation to demonstrate their congruence. This exercise makes a terrific tool for teaching these concepts, or a way to assess learning.
Curated OER
Exploring the Circumcenter of a Triangle
Students construct the circumcenter of a triangle. In this constructing the circumcenter of a triangle lesson plan, students construct a triangle using Cabri Jr. Students draw perpendicular bisectors of the sides of the triangle....
EngageNY
Applying the Laws of Sines and Cosines
Breaking the law in math doesn't get you jail time, but it does get you a wrong answer! After developing the Law of Sines and Cosines in lesson 33 of 36, the resource asks learners to apply the laws to different situations. Pupils must...