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MathGroup Archive 2004

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Re: Inverse of "PowerExpand"

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51981] Re: Inverse of "PowerExpand"
  • From: Karl_boehme_9 at msn.com (Klaus G)
  • Date: Sat, 6 Nov 2004 02:07:46 -0500 (EST)
  • References: <cm267l$hdg$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

> Unfortunately FunctionExpand  does not return quite what what we want, 
> although it comes near enough.  In fact can do better by using Simplify 
> with arather perverse ComplexityFunction tries  to make expressions 
> more "complex" rather than simpler: (the resulting function should be 
> called Complexify but unfortunately thsis word is already reserved for 
> a different meaning ;-) )

> Simplify[Log[(a*b)/c],{a>0,b>
>      0,c>0},ComplexityFunction->(1/LeafCount[#]&)]
> 
> log(a)+log(b)-log(c)


PowerExpand[Log[(a*b)/c]]
 
-> Log[a] + Log[b] - Log[c]

without any assumptions...
 
 Klaus G.


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