Monthly Archives: September 2008

Euler’s Rotation theorem in 3D

Any rigid body displacement where a point is fixed is equivalent to a rotation. I saw this neat proof from Don Koks’ Explorations in Mathematical Physics. By the hypothesis [tex] |Ar| = |r| \implies r^t A^t A r = r^t … Continue reading

Posted in Books, Geometry/Topology, Linear Algebra | 1 Comment


While perusing some blogs, while waiting for the rain to stop, I’ve found more evidence to support learning maths than replying on calculators. A TRAFFIC warden gave parking fines to innocent motorists because he did not know how to … Continue reading

Posted in Teaching, Technology | Leave a comment

10,000,000 digit primes

Yes, it is plural because two such primes were found within two weeks. See the press release from GIMPS. I guess we can’t really comprehend how big a 10 million digit number is. My ruler tells me that the normal … Continue reading

Posted in Number Theory | Leave a comment