Re: remove higher orders terms from mathemtica's result
- To: mathgroup at smc.vnet.net
- Subject: [mg90928] Re: remove higher orders terms from mathemtica's result
- From: Alois Steindl <Alois.Steindl at tuwien.ac.at>
- Date: Wed, 30 Jul 2008 03:51:50 -0400 (EDT)
- Organization: Inst. f. Mechanics II, TU Vienna
- References: <g6mqap$nt8$1@smc.vnet.net>
kem <kemelmi at gmail.com> writes: > Hi, > Given this: > > K = (1+vy) (zx+wx) + vx (zy+wy); > Expand[K^2] > > Is it possible to remove automatically the 3rd and 4th orders from the > result of 'Expand[K^2]' ? > > By 3rd order I mean terms like: 2 wy zy vx^2 etc. (all terms with sum > of the degrees of derivatives of u,v,w is = 3) > By 4th order: wy^2 vx^2 etc. (sum of degrees of u,v,w = 4) > > > Thanks Hello, isn't 2 wy zy vx^2 a 4th order term? (I admit, that I don't understand your quatities sufficiently well. What is zy?) You could multiply all variables with a weighting factor epsilon, calculate a Series in epsilon, Normalize, and set epsilon=1. This also helps, if you need other weighting factors (eg. consider w itself as 2nd order). Good luck Alois