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Lesson Plan
Curated OER

Pythagorean Theorem by Graphic Manipulation

For Teachers 7th - 9th
There are many different ways to show a proof of the Pythagorean Theorem.  Here is a nice hands-on paper cutting activity that shows a graphic representation. You can even challenge your young Pythagoreans to come up with their own...
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Lesson Plan
Curated OER

Exploring Pythagorean Theorem

For Teachers 8th
Eighth graders explore the Pythagorean Theorem. They use Geometer's Sketchpad and explore features of various figures. Students use the software to build a figure using the given measurements.
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Lesson Plan
Curated OER

Designing a Quilt Pattern

For Teachers 8th - 12th
Young scholars create and color a one-patch quilt design based upon a regular hexagon. They examine quilts and photos of quilt designs, read a handout, and complete their quilt design on a worksheet.
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Unit Plan
CK-12 Foundation

Ck 12: Elem Math: Determining the Unknown Angle in a Triangle

For Students 3rd - 5th Standards
[Free Registration/Login may be required to access all resource tools.] Students watch a video and attempt practice problems on how to determine a missing angle in a triangle.
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Activity
Texas Instruments

Texas Instruments: Sum of Interior Angles in a Triangle With Cabri Jr.

For Teachers 9th - 10th
Students will discover the sum of the interior angles in a triangle using the Cabri Jr. Application.
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Interactive
Mangahigh

Mangahigh: Shape: Proof of the Sum of the Angles in a Triangle

For Students 9th - 10th Standards
Determine that all angles in a triangle equal 180 degrees.
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Activity
Government of Alberta

Learn Alberta: Math Interactives: Exploring Angles Within a Triangle

For Students 6th - 8th
This multimedia Learn Alberta math resource looks at angles of a triangle in the context of building bikes and choosing bike sizes. The accompanying interactive component lets students explore build different sized triangles while...
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Interactive
Walter Fendt

Walter Fendt: Sum of Angles in a Triangle

For Students 9th - 10th
A short interactive activity to show that the sum of the angles of a triangle is 180 degrees.
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Unit Plan
CK-12 Foundation

Ck 12: Geometry: Angle Measures in Given Triangles

For Students 6th
[Free Registration/Login may be required to access all resource tools.] Find the degree measure of an unknown angle in given triangles.
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Unit Plan
CK-12 Foundation

Ck 12: Elem Math: Determining the Unknown Angle in a Right Triangle

For Students 3rd - 5th Standards
[Free Registration/Login may be required to access all resource tools.] Students watch a video overview and attempt practice problems on finding a missing angle in a right triangle.
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Activity
Texas Instruments

Texas Instruments: Angles of a Triangle

For Teachers 9th - 10th
In this activity, students investigate the sum of the measures of the interior angles of a triangle. They will explore interior angles, and their relationship with the exterior angles of a triangle.
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Unknown Type
Khan Academy

Khan Academy: Find Angles in Triangles

For Students 7th - 8th Standards
Find missing angle measures using the properties of triangles. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video, or receive hints.
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Unit Plan
CK-12 Foundation

Ck 12: Geometry: Exterior Angles Theorems

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] This concept teaches students the sum of exterior angles for any polygon and the relationship between exterior angles and remote interior angles in a triangle....
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Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: 8.g Find the Angle

For Teachers 8th Standards
In this task, 8th graders have to reason with angles and angle measurements, including the sum of the angles in a triangle, to deduce information from a picture. Includes a GeoGebra worksheet that the teacher can use for demonstration...
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Interactive
Calculator Soup

Calculator Soup: Triangle Theorems Calculator

For Students 9th - 10th Standards
Each calculation option has sub-bullets that list the sequence of methods used in this calculator to solve for unknown angle and side values including Sum of Angles in a Triangle, Law of Sines, and Law of Cosines.
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Unit Plan
CK-12 Foundation

Ck 12: Elem Math: Determine Unknown Angles: Isosceles, Scalene, Right Triangles

For Students 3rd - 5th Standards
[Free Registration/Login may be required to access all resource tools.] Students watch a video and attempt practice problems on finding the missing angles in triangles.
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Activity
Math Is Fun

Math Is Fun: Interior Angles of Polygons

For Students 3rd - 8th Standards
Learn what an interior angle of a polygon is and how you can calculate their value in triangles, quadrilaterals, and pentagons. Includes a chart that overviews the "general rule" for determining the sum of internal angles in any polygon...
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Unit Plan
Cuemath

Cuemath: Angle Sum Theorem

For Students 9th - 10th
Explore the world of the angle sum theorem in this mini-lesson. Provides a definition and solved examples that help with understanding their properties. Includes practice questions with answers.
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Activity
Texas Instruments

Texas Instruments: Exterior and Interior Angle Theorem

For Teachers 9th - 10th
In this activity, students investigate the relationship between the exterior angle of a triangle and its remote interior angles. They study the Triangle Sum Theorem and the Exterior Angle Theorem.
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Activity
Varsity Tutors

Varsity Tutors: Hotmath: Algebra Review: Angle Sum Theorem

For Students 9th - 10th
Find a quick, concise explanation of the Angle Sum Theorem. A step by step explanation of the proof is included to help you understand the theorem.
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Activity
National Council of Teachers of Mathematics

The Math Forum: Problems Library Geometry Triangles

For Students 9th - 10th Standards
This site contains a wealth of problems that deal with the basic definitions of medians, altitudes, angle bisectors, and perpendicular bisectors or the defining characteristics of the different types of triangles. There are also...
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Unit Plan
Cuemath

Cuemath: Obtuse Triangle

For Students 9th - 10th Standards
In this mini-lesson, learn about obtuse triangles including the obtuse triangle definition, sides, properties, examples, and other fun facts related to it.
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Unit Plan
CK-12 Foundation

Ck 12: Geometry: Comparing Angles and Sides in Triangles

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] This concept teaches students the relationship between opposite angles and sides in triangles and how to use this relationship to compare triangles. students examine...
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Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: 8.g.a Triangle's Interior Angles

For Teachers 8th Standards
In this task, 8th graders are presented with a drawing of two parallel lines with a triangle touching them at all three of its vertices. They are asked to prove that the sum of the triangles' angles equals 180 degrees. Aligns with 8.G.A.5.