Noyce Foundation
Lyle's Triangles
Try five problems on triangles. Levels A and B focus on shapes that can be created from right triangles. Level C touches upon the relationship between the area of a six-pointed star and the area of each triangle of which it is composed....
Curated OER
Exploring Polygons and The Greedy Triangle
Excellent lesson plan! Anne Linehane's geometry story, The Greedy Triangle, offers an opportunity to practice forming various types of polygons with your learners. Using elastic bands (or Chinese jump ropes),...
Everyday Mathematics
Mathematics Within: Slope and Triangles
Learners discover a method for determining the slope of a line by creating and comparing similar triangles. They fold coordinate grids to make three similar triangles then measure the sides to compare the relationships between the...
Curated OER
Let's Explore the World of Triangles and Quadrilaterals!
Second graders explore the features of triangles and quadrilaterals. In this lesson plan on triangles and quadrilaterals, 2nd graders rotate with their group to five different activities all exploring a different aspect of geometry.
EngageNY
Cyclic Quadrilaterals
What does it mean for a quadrilateral to be cyclic? Mathematicians first learn what it means for a quadrilateral to be cyclic. They then investigate angle measures and area in such a quadrilateral.
Curated OER
Symmetries of a Quadrilateral I
Learners examine the properties of quadrilaterals from the point of view of rigid motion. Different types of quadrilaterals are characterized by their symmetries, so learners explore the symmetries of a described quadrilateral to...
Curated OER
Midsegments of Quadrilaterals
High schoolers explore the concept of quadrilaterals as they find the midsegments of quadrilaterals using Cabri Jr. on a graphing calculator. They find midpoints, slopes, angles, and distances of lines and angles.
Curated OER
Quadrilateral Attributes
Students classify quadrilaterals. In this quadrilateral lesson plan, students identify the characteristics of quadrilaterals. They write their findings in a journal. Students use geoboards to create quadrilaterals from given descriptions.
Curated OER
Investigation - Square Numbers and Triangle Numbers
Fifth graders investigate growth patterns using blocks. In this square and triangle numbers instructional activity, 5th graders predict sizes of larger triangles and squares based on numerical patterns they observed while building.
Curated OER
Triangle Island
Students calculate the altitude of triangles. In the web based lesson, students explore the interior distance from a given point in a polygon to its side. They compute the sum of these lengths. Students read life application problems...
Curated OER
Investigating Area Relationships
Learners investigate the area of various figures. They construct triangles and quadrilaterals using Cabri Jr. and discuss the relationships between different angles, side lengths, and figures.
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...
Illustrative Mathematics
All vs. Only Some
All shapes have certain defining attributes that set them apart from others. In order to understand this, young mathematicians look at examples and non-examples of triangles, rectangles, and squares, working as a whole class to create...
Mathematics Assessment Project
Evaluating Statements About Length and Area
Class members complete an assessment task by identifying whether statements about triangles and quadrilaterals are always true, sometimes true, or never true. They then participate in a sorting activity with the same objective.
Curated OER
Creating a Cyclic Quadrilateral
Identify and make conjecture about properties of cyclic quadrilaterals. Students use the TI Navigator to create different shapes and draw conclusions.
Curated OER
An Introduction to Quadrilaterals
Learners explore different types of quadrilaterals. Students define the terminology used with quadrilaterals. They create particular quadrilaterals based on specific characteristics of the quadrilaterals using an online tool.
Curated OER
Area of Rectangles and Triangles
Eighth graders practice calculating the perimeter of different shapes. As a class, they work together to calculate the area of rectangles and triangles using the proper formula. To end the lesson, they determine how many feet are in a...
Curated OER
Zome System
Get hundreds of interactive activity plans using the Zome Modeling System. Among dozens of lessons, a first exposure to similar triangles can be very visual for the learner. Here, young geometers explore the number of different shapes...
Illustrative Mathematics
Sum of Angles in a Polygon
How can learners use algebra to solve a geometry problem? Help learners create an equation that shows the relationship between the number of sides of a polygon and the sum of the interior angles. Students are asked to divide the...
EngageNY
Ptolemy's Theorem
Everyone's heard of Pythagoras, but who's Ptolemy? Learners test Ptolemy's Theorem using a specific cyclic quadrilateral and a ruler in the 22nd installment of a 23-part module. They then work through a proof of the theorem.
Mathematics Vision Project
Module 5: Modeling with Geometry
Solids come in many shapes and sizes. Using geometry, scholars create two-dimensional cross-sections of various three-dimensional objects. They develop the lesson further by finding the volume of solids. The module then shifts to finding...
Concord Consortium
Divisions
Divide and conquer the geometry problem. Young scholars consider how to subdivide triangles into smaller ones that have equal areas. They must apply their knowledge of medians to help accomplish the task.
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
Applied Science - Science and Math (K) Lab
In this shape lesson, learners cut out tangram shapes and create different pictures with them. They look at 3-D shapes as well. There is a nice, hands-on component built into this lesson.