Re: Combine sqrts in denominator

*To*: mathgroup at smc.vnet.net*Subject*: [mg122416] Re: Combine sqrts in denominator*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Fri, 28 Oct 2011 05:33:11 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201110271032.GAA08881@smc.vnet.net>*Reply-to*: murray at math.umass.edu

Forget about the (otherfunctions) factor and look just at: expr = 1/(Sqrt[-h + Sqrt[h^2 + r^2]]*Sqrt[h + Sqrt[h^2 + r^2]]) This does _not_ always equal 1/r. For example: expr /. {h -> I, r -> -2} // Simplify gives 1/2 rather than 1/(-2) as output. Perhaps you want: expr // Simplify[#, h >= 0 && r >= 0] & On 10/27/11 6:32 AM, Tom D wrote: > I'm doing a calculation that results in terms of the form > > 1/ Sqrt[ -h + Sqrt[h^2 + r^2]] * 1/Sqrt[h + Sqrt[h^2 + r^2]] * (other > functions) > > One sees that this simplifies to (other functions)/r. > > It would helpful to make Mathematica perform this simplification, but > I have not been able to get Simplify[] or FullSimplify[] or anything > else to do it. > > How would I be able to do this? > > Thanks, > Tom > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**Combine sqrts in denominator***From:*Tom D <tomdickens@att.net>