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MathGroup Archive 1999

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Re: Solve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18880] Re: Solve
  • From: Harald Giese <giese at dkrz.de>
  • Date: Sun, 25 Jul 1999 03:30:13 -0400
  • Organization: Institut fuer Meereskunde, Universitaet Hamburg
  • References: <7n6al2$h8g@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

steffenz at mail.fo.fh-koeln.de wrote:
> 
> Hi !
> 
> I try to use solve but mathematica neads houers eating up all memory
> but did not finish.
> Is there any mistake in my programming or is this problem to
> complicate?
> 
> bye
> 
> Steffen
> 
> Einheits[vec_]:=vec/Sqrt[vec.vec];
> Wink[vec1_,vec2_]:=ArcCos[Einheits[vec1].Einheits[vec2]];
> 
> v[alp_,bet_]:=Einheits[{Tan[bet],Tan[alp],1}];
> vlam[alp1_,bet1_,alp2_,bet2_]:=Einheits[-v[alp1,bet1]+v[alp2,bet2]];
> quell[vec_,fac_:1.3]:=Einheits[vec*{1,1,1/fac}];
> 
> Solve[{Evaluate[Wink[v[a12,b12],v[a22,b22]]==Wink[v[a11,b11],v[a21,b21
> ]]],
> Evaluate[vlam[a12,b12,a22,b22]==quell[vlam[a11,b11,a21,b21]]]},{a11,b1
> 1,a21,
>     b21}]


Hi Steffen,

Have you looked at the expressions you transfered to Solve? Probably
not: 
There are about 180 lines with three tangent-functions per line!

Try to simplify the equations first:
eq1 = Evaluate[Wink[v[a12,b12],v[a22,b22]]==Wink[v[a11,b11],v[a21,b21]]]
eq2 = Evaluate[vlam[a12,b12,a22,b22]==quell[vlam[a11,b11,a21,b21]]]

smpEq1 = Simplify[eq1]
smpEq2 = Simplify[eq2]

Solve[{smpEq1, smpEq2}, {a11,b11,a21,b21}]

Good luck!

Harald

-- 
Harald Giese
Email: giese at dkrz.de
> NEUE TELEFON-NUMMER | NEW PHONE-NUMBER <
Phone: +49 (0)40 42838 5796; Fax: +49 (0)40 5605724
Institut fuer Meereskunde der Universitaet Hamburg
(Institute of Oceanography of the University of Hamburg)
Troplowitzstrasse 7, D-22529 Hamburg


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