CK-12 Foundation
Pythagorean Theorem to Classify Triangles: Missing Angles
Learn to use the Pythagorean Theorem with non-right triangles. Pupils use the interactive to discover the relationship between the lengths of sides for acute and obtuse triangles. They compare the squares of the sides of the triangles to...
Math Mammoth
Measuring Angles
The first of two pages displays various angles as the measure of degrees of a circular arc. An explanation is written, and learners are asked to model each by holding up two pencils as the rays. The second page provides instruction on...
K-5 Math Teaching Resources
2-D Shape Cards
Add some visual support to your elementary geometry lessons with this set of printable shape cards. From triangles and squares to octagons and nanogons, this simple resource can be used in countless ways to develop children's knowledge...
Curated OER
Transformations in the Coordinate Plane
Your learners connect the new concepts of transformations in the coordinate plane to their previous knowledge using the solid vocabulary development in this unit. Like a foreign language, mathematics has its own set of vocabulary terms...
Curated OER
Investigating AAS
Students investigate the theorems of ASA, AAS, AAA and ASA. In this geometry lesson, students discuss the theorems of triangles and how it is used to solve for missing sides or angles. They review how two angles are formed by two rays...
Curated OER
Angles, Triangles, Quadrilaterals, Circles and Related
Students classify angles. In this angles lesson, students explore the characteristics of angles, triangles, quadrilaterals and circles. They identify polygons and sing a classifying angles song. Students participate in a manipulative...
Curated OER
Basic Right Triangles
Elementary schoolers examine the attributes of triangles. In this triangle lesson plan, learners compare regular triangles and right triangles. They explore vertices and angles and investigate obtuse and acute angles. Pupils draw...
Ohio Department of Education
Describing and Creating Plane Figures - Grade One
Young mathematicians draw, create, and describe different shapes using triangles. They discuss attributes of the original and created shapes. Pupils classify the created shapes and draw and write in mathematics journals to communicate...
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...
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...
Curated OER
Finding Perimeter and Area
Geometers find the perimeter and area of rectangles. They discuss the definitions and characteristics of rectangles and squares. In groups, they use yarn to discover the perimeter of squares and rectangles. They count cubes to explore...
Arizona State University
Tricorn Triangles
Help your learners examine triangles. Pupils explore the different sizes and measurements of triangles. They discover triangles can be isosceles or scalene, and examine the attributes of triangles. Here is the website where you can...
Curated OER
Angle-Side Relationships
Students calculate the different sides and angles of a triangle. In this geometry lesson, students use triangular properties to define the relationship between two triangle. They identify missing angles using the interior angle theorem.
Curated OER
Sin, Cos and Tangent
Students find the identity o sine, cosine and tangent. In this precalculus instructional activity, students solve and identify the different parts of a right triangle. They use the ratios of the Pythagorean Theorem to find the missing...
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
Parallelism in Our Everyday World: Parallel Lines and Beyond
Young scholars broaden their outlook on geometry in their everyday environment. They explore the properties of parallel lines and parallelograms and discover ways to prove the existence of parallel lines and discuss the concept of...
Curated OER
Finding the Area of an Equilateral Triangle
The problem seems simple: find the area of the equilateral triangle whose sides are each length 1. In fact, this same problem is solved in 8th grade, addressing a different Common Core standard, using the formula for area of a triangle...
Curated OER
Quadrilaterals: Four-sided Figures
Fifth graders engage in a variety of hands-on and technology-rich activities involving the classification of quadrilaterals. They utilize protractors and rulers to investigate the characteristics of various types of quadrilaterals. They...
Curated OER
Geometry is Fun and EverywhereGeometry, You Don’t Care? Geometry is Fun and Everywhere
Third graders investigate shapes in our world. In this geometry lesson, 3rd graders describe plane and solid shapes and identify angles, solid objects and lines of symmetry. Students use online resources, graphic organizers and conduct...
Curated OER
Marshmallow Geometry
Third graders create 2D and 3D shapes using marshmallows and toothpicks. In this geometry instructional activity, 3rd graders create their shapes and document the number of faces, edges, corners, angles, and sides. They share one shape...
Curated OER
Pythagorean Theorem
Students solve problems using the Pythagorean Theorem. In this geometry lesson, students identify different parts of a right triangle. They use the Pythagorean Theorem to calculate missing angles and sides.
Curated OER
Triangle Inequality Theorem
Learners 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...
Curated OER
Geoboard Ideas
Learners build polygons on their geoboards. In this geometry lesson plan, students build and then draw it on paper and label it. Learners then switch with a partner to try an make a symmetrical shape.
Curated OER
Roping Quadrilaterals
Learners explore with quadrilaterals. In this roping quadrilaterals lesson, students work in cooperative groups to play the game, "Question, please!" in order to identify, describe, compare and classify quadrilaterals....