The above shell is a copy of Don's watercolor painting of The Nautilus shell; it is Don's logo. The shell is beautiful,  its shape a mathematical curve, and can be obtained from conchking. Also see the equation for the shellmaking a spiral , IES java applet making a Nautilus, Xah Lee's work on spirals (and other curves) and student work on the growth of the Nautilus (chapter 6), and Don compares the Spirals of the Nautilus shell, the Fibonacci numbers, and the Equal Tempered Chromatic Music Scale .

Don retired from The Math Program

as of May 30, 2014

Don's new telephone #  is 217.840.4559, same email address:    

doncohenmathman@gmail.com

Don's new address: 1905 S. Prairie Winds Dr. Apt. 204, Urbana, IL 61802


On the last day of the school year 2013-2014, Sue, below, received an award for the most improved math student in 5th grade at Holy Cross elementary school. Read what Grandma had to say!



                            Meredith was given this award from her HS math teacher. Don tutored Meredith during the 2013-2014 school year-- 2x/week. It's great when his students get awards.