History Resources
The Euler Archive
This is a great on-line resource hosted by the Math Department at Dartmouth University: a comprehensive collection of the works of (and about) Leonhard Euler.
http://www.math.dartmouth.edu/~euler/
Euler, indisputably one of the greatest mathematicians in history, authored over 800 papers in his lifetime, touching on every area of mathematics then in existence. In addition, Euler made significant contributions to physics, astronomy, and applied sciences as well.
The archive features historical and biographical information, related resources, and digital copies of over 800 original documents.
Challenge Geometry Teaching
Quadrilateral Challenge — A Solution
Here is one approach to answering the quadrilateral challenge posed earlier. In summary, the challenge was to prove or disprove the following statement: A quadrilateral with a pair of congruent opposite sides and a pair of congruent opposite angles is a parallelogram.
I offer this disproof without words.
By starting with an isosceles triangle, cutting it, rotating one of the pieces, and gluing it back together, we have constructed a quadrilateral with one pair of congruent opposite sides and one pair of congruent opposite angles that it is not necessarily a parallelogram!
Geometry Resources
Geometric Estimation Game
This is a ton of fun: a geometric estimation game!
Given a variety of scenarios, your job is to eyeball various geometric constructions like midpoint, angle bisector, and point of convergence.
The game not only times you, but it measures your error in units and keeps a running tally on your average error!
What a great way to develop geometric intuition! Or while away a little bit of time.
Challenge NYT
Math Quiz: NYT Learning Network
Through Math for America, I am part of an on-going collaboration with the New York Times Learning Network. My latest contribution, a Test Yourself quiz-question, can be found here:
https://learning.blogs.nytimes.com/2011/12/14/test-yourself-math-dec-14-2011/
This problem is related to the record low yields of acorns this year in the Northeast United States.