Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: dot and cross product of complex numbers with extra values. Date: Tue, 13 Dec 2011 23:15:09 +0000 (UTC) Organization: The MathWorks, Inc. Lines: 27 Message-ID: <jc8m9t$83a$1@newscl01ah.mathworks.com> References: <jc8etj$e54$1@newscl01ah.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: www-05-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: newscl01ah.mathworks.com 1323818109 8298 172.30.248.37 (13 Dec 2011 23:15:09 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Tue, 13 Dec 2011 23:15:09 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 1187260 Xref: news.mathworks.com comp.soft-sys.matlab:752266 "Johny Salvo" <johnysalvo@yahoo.com> wrote in message <jc8etj$e54$1@newscl01ah.mathworks.com>... > Hi, I need to find dot and cross products of a two complex number. > I searched matlab help and matlab central, but could not get much about this kind of complex values. > a = 3i + 5j + 7k > b = -2i + 3j –k > > so, I wonder that at this point, if I say > dot(a,b) for the doct product and a*b for cross product > dot(a,b) gives 8 > a*b gives -8. > > I do not now the real value of 'k', but for any value of k, solutions are not change. > > I wonder if I am on thr right way, and these results are correct ? > > Can anyone help me on this and show any better way of solving this , please. - - - - - - - - - Unless I miss my guess, you are confusing the i used to denote imaginary and complex numbers, with the i, j, k unit orthogonal vectors used in ordinary (Gibbs) three dimensional vector analysis. In the vector analysis sense your vectors a and b have all real components, [3,5,7] and [-2,3,-1] and matlab's 'dot' and 'cross' functions will readily give their dot (scalar) and cross (vector) products. These are not what you show. See: http://en.wikipedia.org/wiki/Dot_product http://en.wikipedia.org/wiki/Cross_product If you are discussing quaternions, the 'dot' and 'cross' products are not the same as quaternion multiplication. Quaternions are an extension of complex numbers into four-dimensinal space. See http://en.wikipedia.org/wiki/Quaternion Roger Stafford