Explore Geometry 
Bisected Chord 
A chord is a line segment where the endpoints of the segment are on a
circle. When one bisects the chord of a circle, some interesting
properties emerge. 
Explore Geometry 
How
Eratosthenes Calculated the Circumference of the Earth 
While Eratosthenes was not the first to estimate the circumference
of the earth, his was the most accurate of the ancient estimates. Here
is how he did it.
PDF Version 
Geometric Proofs 
Proof:
The summit angles of a Saccheri Quadralateral are Congruent 
A Saccheri Quadralateral is an important construction in Hyperbolic
Geometry. It can be used to show many useful properties of Hyperbolic
Geometry.

Geometric Proofs 
Proof:
The segment connecting the midpoints of the summit and base line
segments of a Saccheri Quadralateral is perpendicular to both. 
A Saccheri Quadralateral shows what parallel means in Hyperbolic
Geometry.

EBooks 
Chinese
Education From a Western Viewpoint by Yen Sun Ho 
I find this to be an interesting book. Through Yen Sun Ho's comparison
of Chinese education to European and U.S. education, he provides a snapshot
of education in 1912. Of particular interest to me was the comparison of
the cultures and philosophies that surrounded these educational systems.

Worksheet 
Chinese Proof
of the Pythagorean Theorem 
The Chinese proof of the Pythagorean Theorem is easier to teach
and understand than the Euclid's proof from his book Elements. This
worksheet includes a cutout to reproduce the proof with paper shapes.

Worksheet 
Cramer's Rule Worksheet 
This worksheet is a learning aid for teaching Cramer's rule.

Worksheet 
How Eratosthenes Calculated the Circumference of the Earth. 
This one page worksheet briefly reviews the history about and methods
used by Eratosthenes when he calculated the circumference of the earth.

Lesson Plan 
Finding the Circumference of the Earth 
This lesson focuses on using the estimation of the circumference of the
earth to reinforce basic geometric properties of circles and parallel lines.
The lesson continues with using Eratosthenes method to estimate the
circumference of the earth.

Worksheet 
Circumference of the Earth Worksheet 
This worksheet provides a framework for using Eratosthenes method for measuring
the circumference of the earth. HERE ******************************************************

Lesson Plan 
Introduction to Negative Numbers 
This lesson introduces the student to negative numbers using the
concepts of magnitude and direction in both visual and kinesthetic
frameworks.

Rubric 
Rubric for negative numbers creative activity. 
This rubric accompanies the lesson Introduction to Negative Numbers.

Rubric 
Rubric for student's descriptions of negative numbers. 
This rubric accompanies the lesson Introduction to Negative Numbers.

Geometric Proofs 
Proof  A trapezoid is isosceles if
and only if the two base angles are equal. 
An isosceles trapezoid is a trapezoid where the nonparallel sides are
equal in length.
