q! CZCZCZCZCZC"math-fun@mailman.xmission.com" "math-fun" 9-MAY-2003 11:57:36.00 To: IN%"math-fun@mailman.xmission.com" "math-fun" CC: Subj: RE: [math-fun] horizontal and vertical flip in Dihedral group (D4) Return-path: <math-fun-bounces@mailman.xmission.com> Received: from clyde.concordia.ca (clyde.Concordia.CA [132.205.1.1]) by vax2.concordia.ca (PMDF V6.2 #30559) with ESMTP id <01KVOQNGVEQU000ZVC@vax2.concordia.ca> for mckay@vax2.concordia.ca (ORCPT mckay@vax2.concordia.ca); Fri, 09 May 2003 11:57:35 -0400 (EDT) Received: from mailman.xmission.com (mailman.xmission.com [198.60.22.29]) by clyde.concordia.ca (8.12.9/8.12.9) with ESMTP id h49FvOa7142235 for <mckay@vax2.concordia.ca>; Fri, 09 May 2003 11:57:24 -0400 (EDT) Received: from localhost ([127.0.0.1] helo=mailman.xmission.com) by mailman.xmission.com with esmtp (Exim 3.35 #1 (Debian)) id 19EAFJ-0007cg-03; Fri, 09 May 2003 09:57:17 -0600 Received: from web40702.mail.yahoo.com ([66.218.78.159]) by mailman.xmission.com with smtp (Exim 3.35 #1 (Debian)) id 19EA72-0007Q0-00 for <math-fun@mailman.xmission.com>; Fri, 09 May 2003 09:48:44 -0600 Received: from [66.81.121.30] by web40702.mail.yahoo.com via HTTP; Fri, 09 May 2003 08:48:14 -0700 (PDT) Date: Fri, 09 May 2003 08:48:14 -0700 (PDT) From: Eugene Salamin <gene_salamin@yahoo.com> Subject: Re: [math-fun] horizontal and vertical flip in Dihedral group (D4) In-reply-to: <5.2.0.9.2.20030509042616.039cedb0@mail.attbi.com> Sender: math-fun-bounces@mailman.xmission.com To: math-fun <math-fun@mailman.xmission.com> Errors-to: math-fun-bounces@mailman.xmission.com Reply-to: math-fun <math-fun@mailman.xmission.com> Message-id: <20030509154814.63853.qmail@web40702.mail.yahoo.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Precedence: list X-BeenThere: math-fun@mailman.xmission.com X-Mailman-Version: 2.1.1 X-Scanned-By: MIMEDefang 2.26 (www . roaringpenguin . com / mimedefang) List-Post: <mailto:math-fun@mailman.xmission.com> List-Subscribe: <http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun>, <mailto:math-fun-request@mailman.xmission.com?subject=subscribe> List-Unsubscribe: <http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun>, <mailto:math-fun-request@mailman.xmission.com?subject=unsubscribe> List-Archive: <http://mailman.xmission.com/cgi-bin/mailman/private/math-fun> List-Help: <mailto:math-fun-request@mailman.xmission.com?subject=help> List-Id: math-fun <math-fun.mailman.xmission.com> Original-recipient: rfc822;mckay@vax2.concordia.ca The dihedral groups contain only proper rotations, no reflections or inversions. D4 has 8 elements. It has the 4-element subgroup C4 of rotations about the z-axis, and four 180-degree rotations about axes that lie in the xy-plane and are separated by 45 degrees. --- Ray Tayek <rtayek@attbi.com> wrote:

hi, iirc, the elements are : e, r, r2, r3, h, v, d1, and d2.

does h flip about the x or y axis?

is d1 / or \?

or are there a more mnemonic set of element names?

thanks

--- ray tayek http://tayek.com/ actively seeking mentoring or telecommuting work vice chair orange county java users group http://www.ocjug.org/ hate spam? http://samspade.org/ssw/

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