Assessment
Balanced Assessment

Triangle in Circle

For Students 6th - 8th
Even kindergartners can draw triangles in circles, but the assessment task requires a bit more geometric knowledge. Scholars investigate triangles that have a diameter of a circle as one of its sides. They must consider triangles that...
Lesson Plan
Illustrative Mathematics

Are These Right?

For Teachers 3rd - 5th Standards
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...
Lesson Plan
EngageNY

Base Angles of Isosceles Triangles

For Students 9th - 10th Standards
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...
Assessment
Mathematics Assessment Project

Circles in Triangles

For Students 9th - 12th Standards
Circles, and triangles, and tangents, oh my! In the assessment task, learners first answer questions leading to the radius of an inscribed circle for a given right triangle. They then use the result to independently determine the...
Lesson Plan
Illustrative Mathematics

Finding Areas of Polygons, Variation 1

For Teachers 5th - 9th Standards
An exercise in finding the area of polygons by decomposing into triangles and composing into rectangles is the focus of this resource. Make several copies of the worksheet for each participant. Ask learners to use colored pencils to...
Lesson Plan
West Contra Costa Unified School District

Investigating Special Right Triangles

For Teachers 9th - 12th
Scholars first investigate relationships in the side lengths of 30°-60°-90° triangles and 45°-45°-90° triangles. This knowledge then helps them solve problems later in the lesson plan about special right triangles.
Unit Plan
Buffalo State

A Five Day Approach to Using Technology and Manipulatives to Explore Area and Perimeter

For Teachers 3rd - 6th Standards
Young mathematicians build an understanding of area and perimeter with their own two hands in a series of interactive geometry lessons. Through the use of different math manipulatives, children investigate the properties of...
Lesson Plan
Illustrative Mathematics

Running on the Football Field

For Teachers 7th - 9th Standards
Make your class into Pythagorean theorem fanatics in no time. What a great resource to get your sports enthusiasts into the math game! Read the commentary so you can you can strategize how to apply the three math practices.
Worksheet
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K12 Reader

Shapes on a Plane

For Students 2nd - 3rd Standards
Geometric shapes are the focus of a comprehension exercise that asks readers to examine a short passage about planes, circles, triangles, and rectangles, and then to respond to a series of questions about the article.
Interactive
DocsTeach

Analyzing Photographs of the Triangle Shirtwaist Factory Fire

For Teachers 4th - 8th Standards
While a catalyst for the labor movement, 146 people lost their lives in the Triangle Shirtwaist Factory Fire in 1913. A series of photographs of the aftermath of the tragedy help young historians consider the impact of the fire. The...
Interactive
CK-12 Foundation

Distance Formula: Right Triangles

For Students 8th - 10th Standards
Go the distance with a far out resource. Individuals use an interactive to create right triangles on a coordinate plane to help find distance between two points. Challenge questions aid them in developing the distance formula.
Interactive
CK-12 Foundation

Angle-Angle-Side Triangles: Garden Gate

For Students 10th - 12th Standards
Good fences make good gardens. Individuals use an interactive to see how angles and sides relate in a triangular-shaped garden fence. They apply the Law of Sines to find the length of the garden gate (third side of triangle) given two...
Instructional Video5:17
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Flipped Math

Unit 3 Review: Parallell and Perpendicular Lines

For Students 9th - 12th Standards
Learners watch a quick review on the Parallel and Perpendicular Lines unit. The pupils work through ten review problems ranging from identifying types of angles formed by parallel lines and transversals to writing equations of parallel...
Lesson Plan
EngageNY

Similar Triangles in Circle-Secant (or Circle-Secant-Tangent) Diagrams

For Teachers 9th - 12th Standards
First angle measures, now segment lengths. High schoolers first measure segments formed by secants that intersect interior to a circle, secants that intersect exterior to a circle, and a secant and a tangent that intersect exterior to a...
Lesson Plan
EngageNY

The Volume Formula of a Pyramid and Cone

For Teachers 9th - 10th Standards
Our teacher told us the formula had one-third, but why? Using manipulatives, classmates try to explain the volume formula for a pyramid. After constructing a cube with six congruent pyramids, pupils use scaling principles from...
Handout
Curated OER

Series Review Sheet

For Students 9th - 12th Standards
Save an infinite amount of time and enjoy this pre-made series formula guide. Arithmetic and geometric formulas are all included as well as Pascal's Triangle and examples of how the Binomial Theorem expands. 
Lesson Plan
Curated OER

Similar Triangles and Proportions

For Teachers 9th - 12th Standards
Pupils investigate similar triangles and proportions as they make conjectures about the length of sides of similar triangles. For this lesson plan, have your class construct similar triangles using Cabri Jr so that they share a common...
Lesson Plan
Curated OER

Indirect Proof and Inequalities in One Triangle

For Teachers 10th
In this geometry worksheet, 10th graders order the sides and angles of a triangle and determine the range of the third side of a triangle given the lengths of two sides.  The one page worksheet contains sixteen questions. ...
Lesson Plan
Curated OER

Triangle Midsegment

For Teachers 9th - 12th Standards
Learn how to calculate the length and midsegments of triangles. Learners differentiate between similar and congruent triangles. They create a spreadsheet with their findings.
Interactive
Curated OER

Triangle Fundamentals Multiple Choice

For Students 8th - 10th
For this triangle fundamentals worksheet, students identify possible side lengths of triangles. The first three problems give measurements of the sides, students select the combination that is possible in a triangle. The final three...
Lesson Plan
Curated OER

Incenter of a Triangle

For Teachers 10th
Tenth graders explore the properties of the incenter of a triangle. In this geometry lesson, 10th graders construct a triangle and the angle bisectors of each angle. The dynamic properties of Cabri Jr. allow students to locate and...
Worksheet
Curated OER

The Area of a Triangle

For Students 5th - 6th
In this area of a triangle instructional activity, students solve 30 problems in which the area of triangles are calculated. There is instruction on the page. This is intended for on-line use but can be done on paper.
Lesson Plan
Curated OER

Triangles

For Teachers 6th - 10th
Students identify triangles in the real world and construct their own triangle using drinking straws. They explore abstract triangles and find additional geometric shapes such as trapezoids. Students discuss similar shapes and examine...
Worksheet
Curated OER

Area of Triangle Worksheet

For Students 5th - 6th
In this area worksheet, students find the area of a triangle given the height and the base. They also find the height or base given the area of the triangle. 

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