Re: Forcing functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg51027] Re: [mg51006] Forcing functions*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Sat, 2 Oct 2004 03:17:55 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 1 Oct 2004, at 17:48, Barry Tesman wrote: > Can you "force" Mathematica to not use certain functions? E.g., I > want to give my students some problems to antidifferentiate. One > such problem is: > > Integrate[ x * Sqrt[x^2 + 2x +4], x] > > The answer uses arcsinh. Can one force Mathematica to use natural > log instead? > > Thanks, > Barry > The answer is not really , but.... If you evaluate at the begining of a session: $Post = (If[! FreeQ[#, ArcSinh | ArcCosh], TrigToExp[#], #] &); then Integrate[x*Sqrt[x^2+2x+4],x] (1/6)*(Sqrt[x^2 + 2*x + 4]*(2*x^2 + x + 5) - 9*Log[(x + 1)/Sqrt[3] + Sqrt[(1/3)*(x + 1)^2 + 1]]) You could even put this definiton into an init.m file so that it is evaluated every time Mathematica is run. Andrzej Kozlowski Chiba, Japan http://www.akikoz.net/~andrzej/ http://www.mimuw.edu.pl/~akoz/