Curated OER
Pascal's Triangle
Students explore the concept of Pascal's Triangle. For this Pascal's Triangle lesson, students use an applet called 'Coloring Multiples' to explore Pascal's Triangle. Students develop patterns starting with various numbers in Pascal's...
Curated OER
Circles, Squares, Triangles and Rectangles In Our World
Here is an engaging geometry lesson plan which has students identify the properties of shapes and cut shapes out of magazines. They make cookies using cookie cutters in various shapes.
Curated OER
Triangle Inequality Theorem
Students use the inequality theorem to solve triangles and their properties. In this geometry lesson, students are given spaghetti of different lengths and asked to create triangles. They conclude the necessary length needed to make a...
Willow Tree
Angle Sum Property of Triangles
All triangles have some things in common. Using these properties of triangles, learners find missing angle measures. Scholars use the Angle Sum Property and properties of special triangles throughout the lesson.
Mt. San Antonio Collage
Congruent Triangles Applications
Triangles are all about threes, and practicing proving postulates is a great way to get started. The first page of the worksheet provides a brief introduction of the different properties and postulates. The remaining pages contain...
Bowland
Rods and Triangles
Scholars explore triangles with rods of different lengths. Using rods of 2, 4, 6, 8, and 10 cm class members build as many different types of triangles as they can. They also describe properties of these triangles and determine...
Curated OER
Triangle Congruence
In this triangle congruence worksheet, students review 4 triangle congruence properties and 4 examples. Students are then prompted to complete 15 problems analyzing whether two triangles are congruent and determine by which property.
Illustrative Mathematics
Right Triangles Inscribed in Circles I
One of the basic properties of inscribed angles gets a triangle proof treatment in a short but detailed exercise. Leading directions take the learner through identifying characteristics of a circle and how they relate to angles and...
Curated OER
Find the Perimeter of Triangles
In this perimeter worksheet, students calculate the perimeter of various different triangles. There are four problems to solve.
EngageNY
Properties of Area
What properties does area possess? Solidify the area properties that pupils learned in previous years. Groups investigate the five properties using four problems, which then provide the basis for a class discussion.
EngageNY
Triangle Congruency Proofs (part 1)
Can they put it all together? Ninth graders apply what they know about proofs and triangle congruence to complete these proofs. These proofs go beyond the basic triangle congruence proofs and use various properties, theorems, and...
EngageNY
Base Angles of Isosceles Triangles
Build confidence in proofs by proving a known property. Pupils explore two approaches to proving base angles of isosceles triangles are congruent: transformations and SAS. They then apply their understanding of the proof to more complex...
EngageNY
More on the Angles of a Triangle
Angles and triangles: they're all connected. Uncover the connections between angles in triangles. Scholars learn how to find both exterior and interior angle measures in triangles. The lesson emphasizes the vocabulary related to these...
Concord Consortium
Triangles: Angle Space
Three angles in a triangle, three-dimensional space, it all seems connected somehow. Given several different triangles, pupils use the three angles of the triangle as coordinates to plot points in three-dimensional space. They explore...
Mathematics Assessment Project
Inscribing and Circumscribing Right Triangles
High schoolers attempt an assessment task requiring them to find the radii of inscribed and circumscribed circles of a right triangle with given dimensions. They then evaluate provided sample responses to consider how to improve their...
Curated OER
Exploring the Centroid of a Triangle
Pupils examine the centroid of a triangle as they use Cabri Jr. to construct a triangle and its medians. The dynamic nature of the software allows learners to measure the lengths of the segments in the triangle and conjecture and verify...
Concord Consortium
Always, Sometimes, Never
Do your learners always, sometimes, or never remember the properties of the segments in triangles? Get that number closer to always with a creative lesson analyzing all four segments. Scholars consider a statement about one of the...
EngageNY
Definition and Properties of Volume
Lead a discussion on the similarities between the properties of area and the properties of volume. Using upper and lower approximations, pupils arrive at the formula for the volume of a general cylinder.
Curated OER
Which Triangles are Right
Learners apply properties of right triangles to solve problems. In this geometry activity, students identify axioms and theorems using examples.
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.
Illustrative Mathematics
Placing a Fire Hydrant
Triangle centers and the segments that create them easily become an exercise in memorization, without the help of engaging applications like this lesson. Here the class investigates the measure of center that is equidistant to the three...
Illustrative Mathematics
Are They Similar?
Learners separate things that just appear similar from those that are actually similar. A diagram of triangles is given, and then a variety of geometric characteristics changed and the similarity of the triangles analyzed. Because the...
EngageNY
Law of Sines
Prove the Law of Sines two ways. The ninth segment in a series of 16 introduces the Law of Sines to help the class find lengths of sides in oblique triangles. Pupils develop a proof of the Law of Sines by drawing an altitude and a second...
EngageNY
Informal Proof of AA Criterion for Similarity
What does it take to show two triangles are similar? The 11th segment in a series of 16 introduces the AA Criterion for Similarity. A discussion provides an informal proof of the theorem. Exercises and problems require scholars to apply...