Texas Instruments
Texas Instruments: Opposite Angles in a Cyclic Quadrilateral
This activity uses Cabri Jr. to discover that opposite angles in a cyclic quadrilateral are supplementary
Texas Instruments
Texas Instruments: Special Midpoint Quadrilaterals
Midpoint Quadrilaterals are quadrilaterals that are formed when consecutive midpoints of a quadrilateral are connected. This activity will use Cabri Jr. to investigate what properties an exterior quadrilateral has if its midpoint...
The Math League
The Math League: Figures and Polygons
This site provides definitions of different types of polygons and figures.
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Los Cuadrilateros
In Spanish. Interactive resources and activities that could be used in the classroom either as an introduction or review to a unit dealing with area and perimeter of quadrilaterals.
Jim Loy
Jimloy.com: Saccheri
This site explains the Saccheri quadrilateral and the importance of his work in geometry.
Maths Challenge
Maths challenge.net: Quadrilateral Parallelogram
A "three star geometry problem" requiring knowledge of how to complete geometric proofs and some prior math knowledge. This problem asks to prove that the mid points of any quadrilateral form a parallelogram.
Maths Challenge
Maths challenge.net: Unique Circle Equal Angles
A "three star geometry problem" - requiring the knowledge of biconditional statements and how to prove such problems.
Maths Challenge
Maths challenge.net: Coloured Strings
A "three star geometry problem" - requiring the knowledge of what a cuboid is and a some knowledge of how to do proofs.
Maths Challenge
Maths challenge.net: Parallelogram Property
A "three star geometry problem" requiring knowledge of how to complete geometric proofs properties of parallelogram.
Other
Generalization
Learn how to construct convex polygons and the mathematical foundations of symmetry on this site.
Math Planet
Math Planet: Geometry: Congruent Triangles
Features a definition and a video lesson on congruent triangles with examples. [1:11]
Math Planet
Math Planet: Geometry: Properties of Parallelograms
The properties of parallelograms are explained through examples and a video lesson. [0:53]
National Council of Teachers of Mathematics
Nctm: Illuminations: Diagonals to Quadrilaterals Ii
This resource explores the bisectors of quadrilaterals. The interactive tool allows learners to draw quadrilaterals with perpendicular bisectors, congruent perpendicular bisectors, and congruent bisectors.
Math Open Reference
Math Open Reference: Quadrilaterals
A complete reference guide to quadrilaterals including squares, rectangles, parallelograms, trapezoids, and rhombus. It provides definitions and interactive activities that enhance further explanation.
Math Planet
Math Planet: Geometry: Polygons
A definition, examples, and a video lesson all help to explain polygons. [0:43]
Math Planet
Math Planet: Geometry: More About Triangles
Explores triangles and related vocabulary through examples and a video lesson.
McGraw Hill
Glencoe Mathematics: Online Study Tools: Self Check Quiz on Quadrilaterals
The online assessment demonstrates knowledge of concepts utilized in Geometry. The multiple choice questions test students on quadrilaterals. Topics include rhombus, parallelogram, and interior angles.
McGraw Hill
Glencoe Mathematics: Online Study Tools: Classifying Quadrilaterals
This site gives a short interactive quiz which allows students to self-assess their understanding of the concept of classifying quadrilaterals.
McGraw Hill
Glencoe Mathematics: Online Study Tools: Congruent Polygons
This site gives a short interactive quiz which allows students to self-assess their understanding of the concept of congruent polygons.
Mangahigh
Mangahigh: Shape: Proof of the Sum of the Angles in a Triangle
Determine that all angles in a triangle equal 180 degrees.
Mangahigh
Mangahigh: Shape: Recognize Quadrilaterals
Determine quadrilaterals based on parallel sides.
Mangahigh
Mangahigh: Shape: Recognize Congruent Shapes
Determine whether shapes are congruent or similar.
