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MathGroup Archive 1998

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Ugly Trig Mess

  • To: mathgroup at
  • Subject: [mg13212] Ugly Trig Mess
  • From: Tobias Oed <tobias at>
  • Date: Mon, 13 Jul 1998 07:43:00 -0400
  • Organization: Old Dominion University
  • Sender: owner-wri-mathgroup at

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,
about 500 structures like a.Cross[b,c])

I would like to find a clever algorithm that uses the relations


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

any help is welcome, Tobias

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