Willow Tree
Ratios and Proportions with Congruent and Similar Polygons
Investigate how similar and congruent figures compare. Learners understand congruent figures have congruent sides and angles, but similar figures only have congruent angles — their sides are proportional. After learning the...
West Contra Costa Unified School District
Congruent and Similar Polygons
What's similar about congruent and similar polygons? Young mathematicians first measure the side lengths and angles of given figures. They use these measurements to determine relationships between side lengths and angles of congruent and...
Math Solutions
Shape Sorting: Looking for Green!
Young mathematicians rotate, flip, and sort their way to an understanding of the different attributes of geometric figures. Using transparent yellow and blue shapes, children try to match congruent figures together...
Virginia Department of Education
Side to Side
Congruent figures: two figures that want to be just like each other. Individuals learn to distinguish between figures that are congruent and those that are not. Measuring the lengths of line segments and angles helps in this endeavor.
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...
Cornell University
Constructing and Visualizing Topographic Profiles
Militaries throughout history have used topography information to plan strategies, yet many pupils today don't understand it. Scholars use Legos and a contour gauge to understand how to construct and visualize topographic profiles. This...
EngageNY
Congruence Criteria for Triangles—AAS and HL
How can you prove it? Guide classes through an exploration of two possible triangle congruence criteria: AAS and HL. Learners connect this criteria to those previous learned and also explore criteria that does not work. The lesson plan...
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...
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
Unknown Angles
How do you solve an equation like trigonometry? Learners apply their understanding of trigonometric ratios to find unknown angles in right triangles. They learn the meaning of arcsine, arccosine, and arctangent. Problems include...
Curated OER
Angle Exploration and Classification
Students compare and contrast angles and identify them as acute, obtuse, right, or straight angles. They create rays and angles using uncooked spaghetti, read and discuss key vocabulary terms, and complete a variety of geometry worksheets.
EngageNY
Points of Concurrencies
You say that perpendicular bisectors intersect at a point? I concur! Learners investigate points of concurrencies, specifically, circumcenters and incenters, by constructing perpendicular and angle bisectors of various triangles.
Curated OER
Shapes Galore!
First graders explore two-dimensional shapes. Individually, children follow directions to draw shapes. Learners use shaving cream, geoboards, yarn, marshmallows, and toothpicks to create shapes. As a class, 1st graders brainstorm...
Illustrative Mathematics
Are These Right?
Is that a right triangle or a wrong triangle? Young mathematicians look at eleven different shapes and use a measuring tool of their choice to determine which triangles have right angles. Consider cutting out sets of the shapes to...
EngageNY
Applications of Congruence in Terms of Rigid Motions
Corresponding parts, congruent parts, congruent corresponding parts—what does it all mean? The resource challenges pupils to identify corresponding parts for pairs of figures. It uses examples of figures that undergo rigid...
Curated OER
Angle-Side Relationships
Learners calculate the different sides and angles of a triangle. In this geometry instructional activity, students use triangular properties to define the relationship between two triangle. They identify missing angles using the interior...
EngageNY
Congruence Criteria for Triangles—ASA and SSS
How do you know if a pair of triangles are congruent? Use the lesson to help class members become comfortable identifying the congruence criteria. They begin with an exploration of ASA and SSS criteria through transformations and...
Virginia Department of Education
Special Right Triangles and Right Triangle Trigonometry
Right triangles are so special! Use special right triangles to discover the trigonometric ratios. Pairs construct special right triangles and find the values of the ratios of the sides. In the process, they discover the ratios stay the...
Curated OER
CSI Investigation of Congruence and Similarity
Students differentiate between similarity and congruence using polygons. In this geometry lesson, students label triangles based on their properties. They find missing sides and angles using the interior sum theorem.
Curated OER
Angles, Triangles, Quadrilaterals, Circles and Related
Students classify angles. In this angles lesson plan, students explore the characteristics of angles, triangles, quadrilaterals and circles. They identify polygons and sing a classifying angles song. Students participate in a...
Curated OER
Introducing Angles
Sixth graders identify, compare and interpret the characteristics of polygons and angles in order to meet spatial sense, geometry and measurement standards. They also sort shapes into three categories, polygons (regular and irregular)...
EngageNY
Incredibly Useful Ratios
Start the exploration of trigonometry off right! Pupils build on their understanding of similarity in this lesson that introduces the three trigonometric ratios. They first learn to identify opposite and adjacent...
EngageNY
More About Similar Triangles
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...
Curated OER
New Angle on Forest Ecology
Students measure and calculate the angle of the sun. They compare the leaf types on the north and south to compare the effects of the sun on the type of vegetation. They complete the activities inside the classroom or on a trip to a...