Website
National Council of Teachers of Mathematics

The Math Forum: Ask Dr. Math: Degrees in a Circle

For Students 9th - 10th
Dr. Math answers a students question as to why a circle contains 360 degrees.
Unit Plan
University of California

University of California: Geometry in Action

For Students 9th - 10th Standards
This page collects various areas in which ideas from discrete and computational geometry (meaning mainly low-dimensional Euclidean geometry) meet some real-world applications.
Activity
National Council of Teachers of Mathematics

The Math Forum: Rotational Symmetry

For Teachers K - 1st
This is a good site for elementary teachers to help educate students about symmetry by using pattern blocks. This link has multiple activities that the instructor could use including technological and standard activities.
Website
National Council of Teachers of Mathematics

The Math Forum: Geometry: Introduction for Primary Students

For Teachers 3rd - 5th
These lessons are designed to guide young children through an introduction to geometry. Children learn to recognize shapes and to create patterns, and explore spatial relations and symmetry. Each activity is aligned to mandated standards.
Handout
University of California

Ucla: Leonhard Euler

For Students 9th - 10th
This University of California site contains a biography of Leonhard Euler.
Unit Plan
Wolfram Research

Wolfram Math World: Coplanar

For Students 9th - 10th Standards
This MathWorld site gives the conditions for an object to be coplanar and a good definition of this term. Gives links to related pages.
Handout
Wolfram Research

Wolfram Math World: Geometric Mean

For Students 9th - 10th
Geometric mean is defined, yet there are no links to help with notation at this MathWorld site. Still a good site to clarify your understanding of this geometric term.
Activity
NumberNut

Number Nut: Shapes, Symbols, and Colors: 2 D Shapes

For Students K - 1st Standards
Did you know that two-dimensional shapes are also called polygons? This lesson describes the various 2-D shapes and includes two interactive games to reinforce skills.
Activity
NumberNut

Number Nut: Shapes, Symbols, and Colors: 3 D Shapes

For Students 3rd - 8th Standards
This lesson describes three dimensional shapes and provides two interactive practice activities.
Activity
NumberNut

Number Nut: Identifying Traits

For Students 3rd - 8th
Investigate the relationship between shapes and identifying traits or characteristics. A concise lesson that explores physical, chemical, and observable traits in the shapes around us. Build on this knowledge by playing the Web Colors...
Activity
Hunkins Experiments

Hunkin's Experiments:how to Measure the Height of a Tree

For Students 3rd - 8th
Hunkin's Experiments is a group of simple cartoon illustrations of scientific principles. Some would work well in the classroom, but others have little value beyond entertaining students. All of the projects are easy to do. This part...
Activity
Wolfram Research

Wolfram Math World: Semiregular Tessellations

For Students 3rd - 8th Standards
This one page Mathworld site has a number of examples of semiregular tessellations. A definition and a small amount of related information is given at the bottom of the page.
Website
National Council of Teachers of Mathematics

The Math Forum: Geometry Discussion Board

For Students 9th - 10th
Math Forum provides a discussion board for geometry topics. The geometry topics are for pre college topics. This site may be found enjoyable for those who like to think about math topics at times other than school.
Handout
Wolfram Research

Wolfram Math World: Map

For Students 9th - 10th
A brief description of a map. There are also many links about related map topics, included on this MathWorld site.
Lesson Plan
Science and Mathematics Initiative for Learning Enhancement (SMILE)

Smile: Learning Ratios & Proportions Through Scale Drawings

For Teachers 9th - 10th Standards
Website which strengthens the conceptual connection between scale drawings and ratios through an activity lesson.
Lesson Plan
Science and Mathematics Initiative for Learning Enhancement (SMILE)

Smile: Measurement Inches

For Teachers 3rd - 5th Standards
This lesson plan for primary students gives students hands-on practice in using a ruler and understanding customary measurements, length and width in inches. Students also create simple one and two digit addition problems related to the...
Handout
Math Is Fun

Math Is Fun: Definition of Congruent

For Students 3rd - 8th Standards
Definition of congruent. Choose the "here's more" link to see examples of a rotation, reflection and translation.
Unit Plan
Vernet -Virtual Education Resources Network

Salon Hogar: Referencia Rapida De Formulas Geometricas

For Students 9th - 10th Standards
This site provides the user with a useful reference to different geometric forms, their elements, formulas, and areas. Entirely in Spanish.
Handout
The Math League

The Math League: Basic Terms: Lines

For Students 3rd - 5th Standards
This tutorial gives a very basic definition of lines.
Unit Plan
The Math League

The Math League: Similar Figures

For Students 6th - 8th Standards
This tutorial explains what similar figures are in geometry and provides examples.
Handout
The Math League

The Math League: Acute Triangle

For Students 3rd - 8th Standards
This site gives the definition of acute triangles.
Handout
The Math League

The Math League: Pentagon

For Students 9th - 10th
This site contains a definition of a pentagon.
Activity
Mr. Martini's Classroom

Mr. Martini's Classroom: Teacher's Figure Library: Geometric Figures

For Students 3rd - 8th Standards
This interactive resource provides an example picture of the geometric figure chosen by students to review.
Activity
Ministry of Education and Universities of the Region of Murcia (Spain)

Ministerio De Educacion Y Ciencia: Geometria Jugando Al Billar

For Students 9th - 10th
In Spanish. Improve your billiard skills by learning the relationship of billiard and Geometry.