Re: "Nice" complex form
- To: mathgroup at smc.vnet.net
 - Subject: [mg131602] Re: "Nice" complex form
 - From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
 - Date: Tue, 10 Sep 2013 03:46:35 -0400 (EDT)
 - Delivered-to: l-mathgroup@mail-archive0.wolfram.com
 - Delivered-to: l-mathgroup@wolfram.com
 - Delivered-to: mathgroup-outx@smc.vnet.net
 - Delivered-to: mathgroup-newsendx@smc.vnet.net
 
Hi,
Can I get
Assuming[a - 4 < 0, Sqrt[a - 4]]
to "simplify" to
I Sqrt[4 - a]
?
Thanks,
Sam
Hi, Sam,
You can.
Assuming[x > 0,
  Simplify[Sqrt[a - 4] /. a -> 4 - x,
   ComplexityFunction -> (Count[{#1}, Times[-1, _], Infinity] &)]] /.
 x -> 4 - a
I Sqrt[4 - a]
Have fun, Alexei
Alexei BOULBITCH, Dr., habil.
IEE S.A.
ZAE Weiergewan,
11, rue Edmond Reuter,
L-5326 Contern, LUXEMBOURG
Office phone :  +352-2454-2566
Office fax:       +352-2454-3566
mobile phone:  +49 151 52 40 66 44
e-mail: alexei.boulbitch at iee.lu