Ugly Trig Mess

*To*: mathgroup at smc.vnet.net*Subject*: [mg13212] Ugly Trig Mess*From*: Tobias Oed <tobias at physics.odu.edu>*Date*: Mon, 13 Jul 1998 07:43:00 -0400*Organization*: Old Dominion University*Sender*: owner-wri-mathgroup at wolfram.com

Hi all, In a calculation I am doing I end up with a long sum of terms (~3000) of the form: f1 a.b + f2 a.Cross[b,c] + f4 a.d b.Cross[a,c] + f5 ... Where a,b,c,d represent vectors (In my problem there are 6 of them, forming about 500 structures like a.Cross[b,c]) I would like to find a clever algorithm that uses the relations a.Cross[b,c]=b.Cross[c,a]=c.Cross[a,b] Cross[a,Cross[b,c]]= (a.c) b - (a.c) b Cross[a.b] Cross[c.d] = a.c b.d - a.d b.c in order to rewrite some of the structures as sums of other structures. I have thought of something recursive but my computer runs out of memory. any help is welcome, Tobias