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
