I just added a second dynamic geometry proof of the Pythagorean theorem on my Web site.Both are proofs "without words", which in reality means that you should use them to generate discussion. Indeed, many words are needed for students to fully grasp what they see, but the words should not come exclusively from the teacher.… Continue reading Pythagorean Proofs
Tag: Manipulatives
Proportional Relationships
One good thing about the Common Core middle school standards is the emphasis on proportional relationships, and the fact that they are approached in a multidimensional way. In addition to "set up a proportion and solve it", which is probably the most common way to teach this, the standards propose multiple representations and a variety… Continue reading Proportional Relationships
The Lab Gear Is Back
World Cup Fever
The World Cup happens mostly during summer vacation, which is unfortunate, because it provides a great context for a geometry exploration.I start my book Geometry Labs with lessons about angles, starting from the very basics, and moving on to the inscribed angle theorem. (The book is available in its entirety as a free download here.… Continue reading World Cup Fever
Completing the Square
New animation: a geometric representation of completing the square. In this post, I present one way to use it as part of an algebra curriculum.Many secondary school teachers figure that the derivation of the quadratic formula by completing the square can be shown to students, but have little hope of any understanding. They… Continue reading Completing the Square
Ripples
Math curriculum ideas expand outward from their originators, like ripples in a pond. In pre-Internet days, it was great to see teachers using photocopies of photocopies of photocopies of worksheets I created, such as "Make These Designs." Nowadays, of course, people can always download and print a fresh copy. One day at an NCTM meeting,… Continue reading Ripples
More Algebra Book Fan Mail
I have some good news for the users of the online version of Algebra: Themes, Tools, Concepts (ATTC, the textbook I co-authored with Anita Wah): all the ATTC PDFs are now searchable, and many of the files are smaller than they used to be. (See below for links.)Amanda Cangelosi, a Mathematics instructor at the University… Continue reading More Algebra Book Fan Mail
Saturday workshop
I will present a workshop at the the Math Teachers' Circle in Palo Alto (at the American Institute of Mathematics.) The topic is area on a lattice, which we will explore on geoboards and dot paper. We will discuss "curricular" classroom applications (the Pythagorean theorem, simplifying radicals) as well as Pick's theorem and its proof,… Continue reading Saturday workshop
A Curriculum Model
The above map is an attempt at a curriculum development model. Traditional pedagogy stays at the top, as it is based on the belief that skills practice and teacher explanations are sufficient to build student understanding. Understanding acquired this way, plus the skills, allow the student to apply the ideas.Would that it were that simple.In… Continue reading A Curriculum Model
Proving Pick’s Formula
Pick's formula is a way to find the area of a geoboard polygon by counting interior pegs and boundary pegs. Students can discover the formula by doing some experimenting under teacher guidance (see Geometry Labs 8.6 or Algebra: Themes, Tools, Concepts 4.12.) I have used this in the classroom for decades, because it is such… Continue reading Proving Pick’s Formula
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