Re: Manipulating square roots

*To*: mathgroup at smc.vnet.net*Subject*: [mg112357] Re: Manipulating square roots*From*: Peter Breitfeld <phbrf at t-online.de>*Date*: Fri, 10 Sep 2010 05:54:47 -0400 (EDT)*References*: <i6crc2$s62$1@smc.vnet.net>

alan wrote: > How can I get mathematica to bring a factor inside a square root? For > instance > a Sqrt(1-(b/a)^2) -> Sqrt(a^2-b^2) (if a is real and a > 0). > Also, how do I get Mathematica to perform the operation in reverse? > To get a under the root is easy: new=Simplify[a Sqrt[1-(b/a)^2], a>0] For the reverse, you might use a rule: new/.Sqrt[a_^2-b_^2]:>a Sqrt[1-(b/a)^2] This will work in this simple case, but fail if e.g. the root is in the denominator, because then the FullForm no longer matches the pattern Sqrt[a_^2-b_^2] -- _________________________________________________________________ Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de