Geometry Vocabulary

I have actually been getting an incredible amount out of reading this math book, thinking about it in a deeper than usual way due to the need to critique whether a person could really understand all the relevant concepts and material from how it is presented, and doing all the problems.

Today I started the "dreaded" geometry chapter, so-called because I had been warned by teachers at the math camp that it was hard to understand. (By this I do not mean that the teachers and I cannot understand it, but that it is hard for 6th grade students to understand, which is the issue.)

Three things I learned from the first bit of the chapter:

(1) My memory of the unit circle is fading. (The book did not present the unit circle, but I was thinking about it as a way of answering some angle measurement problems despite not having a protractor. Arctan is your friend and Google calculator rocks.)

(2) A different proof of the Pythagorean Theorem (see proof #9 on this page for a picture)

(3) The word "tessellation" - a collection of plane figures that fills the plane with no overlaps or gaps. This is a helpful word for applying to those interlocking figures so common in M.C. Escher's work. I had always thought there had to be some kind of term to describe that pattern and am glad to finally know what it is.

I love the tessellated reptiles on the paper in this one: