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Lesson Plan
National Council of Teachers of Mathematics

The Math Forum: Paper Folding Activity

For Teachers 9th - 10th Standards
This is a lesson plan of paper folding as a method of proof. A Java applet version of the activity can be accessed, giving the actual lengths and angle sizes.
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Activity
Maths Challenge

Maths challenge.net: Unique Circle Equal Angles

For Students 9th - 10th Standards
A "three star geometry problem" - requiring the knowledge of biconditional statements and how to prove such problems.
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Unit Plan
Wolfram Research

Wolfram Math World: Rectangle

For Students 9th - 10th
MathWorld provides the definition of a rectangle and the area formula of a rectangle.
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Activity
Maths Challenge

Maths challenge.net: Tiled Floor

For Students 9th - 10th Standards
An area problem involving diagonals of a tiled floor.
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Activity
Maths Challenge

Maths challenge.net: Shaded Square

For Students 9th - 10th Standards
A problem of finding the fraction of a square that is shaded given criterion. Students will have to use their mathematical reasoning and triangle solving skills to solve this area problem.
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Activity
Maths Challenge

Maths challenge.net: Shaded Hexagon

For Students 9th - 10th
A problem with equilateral triangles and area to solve this "Shaded Hexagon" problem. Mathematical reasoning and triangle knowledge will be needed to solve the problem.
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Activity
Maths Challenge

Maths challenge.net: Corner Circle

For Students 9th - 10th Standards
This is a "three star" geometry problem where prior knowledge of circles and triangles is recommended to solve this circle in the corner problem.
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Activity
Maths Challenge

Maths challenge.net: Shaded Cross

For Students 9th - 10th Standards
Find the area of this tilted cross with your geometry skills.
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Activity
Maths Challenge

Maths challenge.net: Curvature of the Earth

For Students 9th - 10th Standards
Distance problem using a spherical radius and height.
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eBook
CK-12 Foundation

Ck 12: Interactive Geometry: 1.7 the Pythagorean Theorem

For Students 9th - 10th Standards
Explore and discover the Pythagorean theorem.
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Website
Other

Antonio Gutierrez: Geometry From the Land of the Incas

For Students 9th - 10th
Discovering the properties of constructions, seeing proofs in action, and viewing problems come to life here with this wonderful use of technology in the classroom. Single steps are explained and illustrated one at a time so that the...
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Handout
Purple Math

Purplemath: How Can 0.9999 = 1?

For Students 9th - 10th Standards
This resource discusses the relationship between '0.999' and '1' and provides various proofs of their equality.
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Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G C Locating Warehouse

For Teachers 9th - 10th Standards
You have been asked to place a warehouse so that it is an equal distance from three roads on a map. Students must fold a paper so that this point is where two folds intersect, and they must explain why their construction works and why...
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Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G C Placing a Fire Hydrant

For Teachers 9th - 10th Standards
You have been asked to place a fire hydrant so that it is an equal distance from three locations on a map. Students must fold a paper so that this point is where two folds intersect, and they must explain why their construction works and...
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Website
National Council of Teachers of Mathematics

The Math Forum: Geometry Turned On

For Students 9th - 10th Standards
This Math Forum site contains many mathematical and geometric explanations and proofs of many different topics that have been done using a geometry software called Geometer's Sketchpad. The explanations are very detailed and clear;...

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