Sorry, I overlooked the two complete answers to the vector product identity.
John Randall schrieb: > Boyko Bantchev wrote: >> On 29 April 2010 22:35, Raul Miller <[email protected]> wrote: >>> <math> \vec{a}\times(\vec{a}\times\vec{b}) = -|\vec{a}|^2\vec{b}</math> >>> >>> Is this a valid property for cross product? If not, why not? >> >> In general, it is not. > >> It follows that aÃ(aÃb)=-a²b only holds when aâ¥b. > > Alternatively, there is Lagrange's formula for the triple product: > ax(bxc)=(a.c)b-(a.b)c > Applying this gives > ax(axb)=(a.b)a-(a.a)b=-(a.a)b only if a.b=0. > > Best wishes, > > John > > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > -- Prof. Dr. M. Schmidt-Gröttrup Hochschule Ulm, Fakultät Grundlagen Prittwitzstr. 10, 89075 Ulm E-Mail: [email protected] Tel: +49 (0) 731 50 28036 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
