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Interactive
Mangahigh

Mangahigh: Number: Proofs

For Students 6th - 8th
Determine the rules of integers and show what you know.
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Activity
Stefan Warner and Steven R. Costenoble

Finite Mathematics & Applied Calculus: Arguments and Proofs

For Students 9th - 10th Standards
The resource investigates arguments and proofs. The tutorial examines validity, Modus Ponens, counterexamples, and Modus Tollens. Students learn about the logic concepts through notes and examples. Practice exercises are included.
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Website
Education Development Center

Making Mathematics: Proof

For Teachers 9th - 10th Standards
This is a site which links to specific techniques of proving including conditional statements, proof by contradiction, mathematical induction, parity arguments, and the pigeonhole principle. The site contains a link to various example...
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Website
National Council of Teachers of Mathematics

The Math Forum: Ask Dr. Math: The Value of Two Column Proofs

For Students 9th - 10th Standards
This site explains why we prove things. The explanation gives real world scenarios and an everyday example of why we should learn how to prove things.
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Interactive
National Council of Teachers of Mathematics

Nctm: Illuminations: Angle Bisector

For Students 9th - 10th Standards
This interactive demonstrates how to bisect an angle.
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PPT
Sophia Learning

Sophia: Counterexamples: Lesson 7

For Students 9th - 10th
This lesson will help a learner understand counterexamples. It is 7 of 7 in the series titled "Counterexamples."
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Website
Cut the Knot

Cut the Knot!: Proofs in Mathematics

For Students 9th - 10th Standards
This site provides an explanation of mathematical proofs. It also has links to different types of proofs.
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Lesson Plan
Michigan State University

Michigan State University: Biometrics: Hand Geometry

For Teachers 9th - 10th Standards
Students use hand geometry to prove their own identification.
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Handout
Wolfram Research

Wolfram Math World: Two Column Proof

For Students 9th - 10th Standards
MathWorld gives a discussion of the use of two-column proofs by high school and middle school students and its relevance to mathematicians.
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Website
Other

English 100: Persuasive Essay

For Students 9th - 10th Standards
This tutorial provides writing instructions and ideas to help the student in preparing a persuasive essay.