Cynthia Lanius

Thanks to PBS for permission to use the Pyramid photo.
On these pages you will find activities for middle or high school geometry. Bookmark this page and check back often. I hope to add at least one activity per month.

Geometry Online

History of Geometry
A Brief Synopsis of Geometry throughout history. Describes the contributions of Egyptians, Babylonians, and Greeks. Includes links to biographies of major contributors to geometry.


Hidden Irrationals (English Version)
(Spanish Version)

What's the rule? Students will find line segments that they can and cannot draw of various irrational lengths, and then find the rule that allows them to draw or not draw. The page should be printed and the segments shaded in.


Hidden Polygons

Students learn to identify various polygons by locating them on triangular gridpaper. The page can be printed and the figures shaded in. Links to other polygon sites are included.

Isosceles Triangle Puzzler
Students use the Isosceles Triangle Theorem to analyze a problem with similar triangles. Answers can be submitted online.

Impossible Triangles
Students use several different rules to determine triangle "impossibilities". Answers can be checked online.

Circles around Pythagoras
Here's a nice problem with a surprising result - the best kind!

SAT-Type Quiz
Students gain familiarity with SAT-type questions. The paper is graded online.

The Golden Ratio
This lesson introduces the golden ratio with a measuring activity. Students will also build a rectangle that approaches the golden ratio.

Experiment with Volume
This lesson uses a demonstration to introduce volume of cylinders.

School-Bus Geometry
This lesson introduces an unusual measurement of distance using a school bus. See a world where circles are squares?!?

A glossary of the geometric terms used in this short course. Please email me with any word that I've not defined that you feel is needed.

Geometry TEKS
The Texas Essential Skills and Knowledge - What the Texas Education Agency specifies students should know and be able to do from this course.

NCTM Principles and Standards

The National Council of Teachers of Mathematics' view of how school geometry should look.

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Copyright 1997-2008 Cynthia Lanius

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