Math Open Reference
Math Open Reference: Congruent Triangles
A complete reference guide to congruent triangles. It provides definitions, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.8 Applications of Quadrilateral Theorems
Explore quadrilateral properties and threorems.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.7 Theorems About Quadrilaterals
Use quadrilateral properties that are unique to parallelograms to prove that the given shape is a parallelogram.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.4 Theorems About Triangles
Discover some theorems about triangles.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.1 Theorems and Proofs
Understand theorems and proofs as they relate to geometry.
Dartmouth College
Dartmouth College: The Different Styles of Euclid and Copernicus
A history of the differences between Euclid's and Copernicus's methods of proving geometric ideas.
Maths Challenge
Maths challenge.net: Cables
This is a proof problem, considered a "three star" geometry problem requiring knowledge of proofs and properties of circles to solve this problem with cables in duct problem.
Maths Challenge
Maths challenge.net: Radical Axis
This is a "three star" geometry problem requiring knowledge of proofs and properties of circles. Students will use the given definition of radical axis and prior knowledges to prove a way to find a radical axis.
Free Math Help
Free Math Help: Special Parallelograms: Squares, Rectangles, and Rhombuses!
Examines special parallelograms. Students learn about a rectangle, rhombus, and square. Definitions and examples with solutions are included.
Math Is Fun
Math Is Fun: Congruent
The resource investigates congruent shapes. Examples and definitions are included.
Free Math Help
Free Math Help: Angles
The lesson investigates different types of angles used in geometry. Definitions and examples are included.
Shmoop University
Shmoop: Basic Geometry: Quadrilaterals
The geometry resource explores quadrilaterals. Descriptions, examples, and practice exercises are included.
Math Is Fun
Math Is Fun: Congruent Angles
Students learn about congruent angles. A definition, example, and tips are included.
Wolfram Research
Wolfram Math World: Postulate
This MathWorld site defines postulates, and explains how and where they are used in mathematics. The site has numerous links to related terms.
Wolfram Research
Wolfram Mathworld: Theorem
This simple MathWorld site defines theorems and briefly explains how a theorem is produced.
Cut the Knot
Cut the Knot!: Proofs in Mathematics
This site provides an explanation of mathematical proofs. It also has links to different types of proofs.
Michigan State University
Michigan State University: Biometrics: Hand Geometry
Students use hand geometry to prove their own identification.
Wolfram Research
Wolfram Math World: Two Column Proof
MathWorld gives a discussion of the use of two-column proofs by high school and middle school students and its relevance to mathematicians.