Here's one that Mathematica (version 9 at least) can't do much with. Log[Tan[x/2 + Pi/4]] - ArcSinh[Tan[x]] Now it could be that this is not the smallest zero-equivalent expression that FullSimplify can't do, but the example appears in a paper by Joel Moses, with the title Algebraic simplification, a guide for the perplexed. in Comm ACM, August 1971. He toyed with the idea of titling it "a guide TO the perplexed". also see the work by this other Moses. Well, not THAT Moses... http://en.wikipedia.org/wiki/The_Guide_for_the_Perplexed RJF On 10/7/2014 4:53 PM, Bill Gosper wrote:

MKleber> On Tue, Oct 7, 2014 at 1:14 AM, Bill Gosper <billgosper@gmail.com <mailto:billgosper@gmail.com>> wrote:

Out[520]= 1/4 Sqrt[(a + b - c) (a - b + c) (-a + b + c) (a + b + c)] --rwg Side issue (Attention eavesdropping kids!): Given %520, how do you define Heron[a_,b_,c_], short of copying and pasting (which may not always be possible)? I'm guessing your solution doesn't create a value Heron[a_,b_,c_]:=1/4 ... , so you won't be able to reexecute the definition when you reload the notebook. How do you get an executable definition? No wonder everybody just copies and pastes!

Heron[A_,B_,C_] := %520 /. {a->A,b->B,c->C} --Michael

-- Forewarned is worth an octopus in the bush. ----- Interesting that you can't just say Heron[a_,b_,c_]:=%520 But your solution only lasts as long as %520 remains thus defined. How do we incorporate the actual radical into the body of Heron? And how do we get it as re-executable text? --rwg -- You received this message because you are subscribed to the Google Groups "mathfuneavesdroppers" group. To unsubscribe from this group and stop receiving emails from it, send an email to mathfuneavesdroppers+unsubscribe@googlegroups.com <mailto:mathfuneavesdroppers+unsubscribe@googlegroups.com>. For more options, visit https://groups.google.com/d/optout.