# Xah Math Blog Archive 2012-08 to 2012-12

Mathematician Robert J Vanderbei made a comment at Geometry: Gallery of Surfaces. He wrote a surface viewer using latest tech WebGL. It's excellent. Check it out at 〔 http://www.princeton.edu/~rvdb/WebGL/minsurf.html 〕 . You will need to use a broweser that supports WebGL, such as Google Chrome.

I can never remember what “xor” do. But now i got a easy way to remember it. xor returns true if the values of two sides differ.

See also: Logical Operators, Truth Table, Unicode

update: Math Font, Unicode, Gothic Letters, Double Struck, 𝔄 𝔅 ℭ

updated links: Great software for Tilings, Patterns, Symmetry

Great Software for Plane Geometry

Understanding Public-Key Cryptography for Beginner

this tweet is going around:

Dear math, i'm sick and tired of finding your x, just accept the fact that she is gone.

It needs a prelude:

dear girls, i had a fight with my x, but i think she loves me still. help me find x^2+1=5. —Math

3 wonderful articles on cycloids. By mathematician physicist John C. Baez.

- Rolling Circles and Balls (Part 1) By John Baez. At http://johncarlosbaez.wordpress.com/2012/08/31/rolling-circles-and-balls-part-1/
- Rolling Circles and Balls (Part 2) By John Baez. At http://johncarlosbaez.wordpress.com/2012/09/03/rolling-balls-and-circles-part-2/
- Rolling Circles and Balls (Part 3) By John Baez. At http://johncarlosbaez.wordpress.com/2012/09/11/rolling-circles-and-balls-part-3/

It mentioned my site a lot. Thanks John.

William Thurston died. (1946 to 2012). Of skin cancer.

I think i first heard of him thru Jeff Week's book 〈The Shapes of Space〉. 〔►see Reading Notes on 〈The Shapes of Space〉〕 I realized that he's one of the world's top mathematician. Though, his work is beyond my understanding.

What Voting Systems are There?

Memories of Kurt Gödel By Rudy Rucker. At http://www.rudyrucker.com/blog/2012/08/01/memories-of-kurt-godel/