Re: Why can't Mathematica tell when something is algebraically
- To: mathgroup at smc.vnet.net
- Subject: [mg108148] Re: [mg108074] Why can't Mathematica tell when something is algebraically
- From: leigh pascoe <leigh at evry.inserm.fr>
- Date: Tue, 9 Mar 2010 06:23:24 -0500 (EST)
- References: <201003081109.GAA03756@smc.vnet.net>
Le 08/03/2010 12:09, mmdanziger a =C3=A9crit : > This isn't the first time that I've encountered something like this in > Mathematica but in my calculations I got a term like this: > > r^2 Sqrt[(r^3 + r + 2)/r] - Sqrt[r^3 (r^3 + r + 2)] > > Which is obviously identically zero. For some reason Simplify or even > FullSimplify can't figure this out. Once you get dependent on > Mathematica these things are pretty disturbing...you forget about your > own knowledge because the program tells you that things are > different. Then you sit there like an idiot checking an algebraic > identity that any beginning precalc student should be able to solve no > problem. > > Is there any way to get Mathematica to "wake up" to these things? It > has such a powerful algebraic engine for most things, why can't it see > something simple like the above? Do you really have to manually > override and tell the program when things should be zero? > > For the time being I'll just sift through and test things by hand but > I can't believe that there isn't a better way. > > Best, > md > > > In[2]:= FullSimplify[r^2 Sqrt[(r^3+r+2)/r]-Sqrt[r^3 (r^3+r+2)]==0] Out[2]= True In[4]:= $Version Out[4]= 7.0 for Microsoft Windows (32-bit) (February 18, 2009) Leigh
- References:
- Why can't Mathematica tell when something is algebraically zero?
- From: mmdanziger <mmdanziger@gmail.com>
- Why can't Mathematica tell when something is algebraically zero?