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Activity
Texas Instruments

Texas Instruments: Numb3 Rs: Slippery Paths

For Teachers 9th - 10th
Based off of the hit television show NUMB3RS, this lesson introduces students to Steiner Points, which are essentially points of concurrency within triangles. This is done in the context of a criminal who needs to place a hideout...
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Activity
Ministry of Education and Universities of the Region of Murcia (Spain)

Ministerio De Educacion Y Ciencia: Actividades Con Las Rectas De Un Triangulo

For Students 9th - 10th
You will find an interactive activity to review the following concepts: altitude, median, angle bisector and points of concurrency in triangles. Five different interactive quizzes are also provided to test your knowledge.
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eBook
Math Planet

Math Planet: Geometry: More About Triangles

For Students 9th - 10th Standards
Explores triangles and related vocabulary through examples and a video lesson.
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Unit Plan
CK-12 Foundation

Ck 12: Geometry: Angle Bisectors in Triangles Intermediate

For Students 9th - 10th
[Free Registration/Login may be required to access all resource tools.] This concept teaches students properties of angle bisectors and how to apply them.
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Handout
Math Open Reference

Math Open Reference: Incircle

For Students 9th - 10th Standards
A complete reference guide to incircles. It provides definitions and examples that enhance further explanation. Includes links to related topics.
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Handout
Math Open Reference

Math Open Reference: The Incircle of a Triangle

For Students 9th - 10th
Learn about the incircle of a triangle with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
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eBook
CK-12 Foundation

Ck 12: Interactive Geometry: 4.5 Theorems About Concurrence in Triangles

For Students 9th - 10th Standards
Find out about some common centers of triangles.
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Activity
PBS

Pbs: Russia's Conversion From Communism to Capitalism

For Teachers 9th - 10th
A case that examines Russia's real-world struggles of converting from a command to market economy. Asks students to consider the pros and cons of both market systems and to formulate explanations for the large gap between the country's...
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Website
Other

Acn: Behavior Modification Charts for Home and School

For Teachers Pre-K - 1st
A variety of charts to be used with children 10 and under from need Association for Comprehensive Neurotherapy. Acrobat Reader to be opened. You may customize each chart to fit your needs and there are several tips to assist in using...
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Unit Plan
Cut the Knot

Cut the Knot: Existence of the Orthocenter

For Students 9th - 10th
This site defines the altitude of a triangle and gives the standard notation for altitudes of a triangle. The site then goes to list several proofs involving altitudes and orthocenters.
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Handout
Math Words

Mathwords: Inscribed Circles

For Students 9th - 10th Standards
Mathwords provides an explanation and a diagram of an inscribed circle. By clicking on any of the highlighted words, you will learn about related terms.
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Handout
Other

University of Evansville: Encyclopedia Triangle Centers

For Students 9th - 10th
This site contains a comprehensive study of triangle centers. Seems more for an advanced level. Provides a list of six links to 1114 centers.
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Website
National Council of Teachers of Mathematics

The Math Forum: Ask Dr. Math: Triangle Centers: Etymologies

For Students 9th - 10th
At this page you will find Dr. Math responding to an inquiry about the relevance of the names of each of the special triangle centers.

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