something (not) funny!

*To*: mathgroup at smc.vnet.net*Subject*: [mg79978] something (not) funny!*From*: dimitris <dimmechan at yahoo.com>*Date*: Fri, 10 Aug 2007 01:42:23 -0400 (EDT)

CAS (Mathematica 5.2 in particular) can be funny sometimes! [Seriously now, I understand the difficulties and the problems that appeared possibly in the following examples and more or less I can figure what goes wrong. Note that one of this examples appeared in a recent post of someone leading him to wonder about the reliability of Mathematica. That's why we should trust but verify results from CASs... Anyway, since for someone-not me!- it is vacation period it is needed some fun!] Version->5.2 Example 1 In[1]:= Timing[FourierTransform[Sech[x*a], x, s]] Out[1]= {58.359*Second, (Sqrt[Pi/2]*Sech[(Pi*s)/(2*a)])/a} However, In[2]:= TimeConstrained[FourierTransform[Sech[x*Log[2]], x, s], 300] Out[2]= $Aborted Example 2 In[4]:= TrigToExp[Sech[x*a]] FourierTransform[%, x, s] Out[4]= 2/(E^((-a)*x) + E^(a*x)) Out[4]= (Sqrt[Pi/2]*Sech[(Pi*s)/(2*a)])/a In[5]:= TrigToExp[Sech[x*Log[2]]] FourierTransform[%, x, s] Out[5]= 2/(2^(-x) + 2^x) Out[5]= FourierTransform[2/(2^(-x) + 2^x), x, s] Dimitris