Re: integration

*To*: mathgroup at smc.vnet.net*Subject*: [mg95967] Re: integration*From*: dimitris <dimmechan at yahoo.com>*Date*: Sat, 31 Jan 2009 01:12:37 -0500 (EST)*References*: <glvkh7$e73$1@smc.vnet.net>

On 30 =C9=E1=ED, 21:30, t.p.ni... at open.ac.uk wrote: > Hi, I don't use mathematica but the other day I wanted to solve an > integral and I'm out of practice so I went on-line to a mathematica > based integrator. > > http://integrals.wolfram.com/index.jsp > > I typed in 1/sqrt(x^2-b^2) this should have an integral of cosh^-1(x/ > b). Ok, so it didn't recognize cosh but its answer was (I think) > wrong. it comes back with ln(x+sqrt(x^2-b^2)) it seems to have > overlooked a quotient of b in the log. > > Is this a general problem with mathematica or just the on-line version > or is it me? Everything is ok! In[683]:= Integrate[1/Sqrt[x^2 - b^2], x] D[%, x] // Together(*check*) Out[683]= Log[x + Sqrt[-b^2 + x^2]] Out[684]= 1/Sqrt[-b^2 + x^2] Dimitris