Re: Mathmatica Problem...

*To*: mathgroup at smc.vnet.net*Subject*: [mg14355] Re: [mg14320] Mathmatica Problem...*From*: David Withoff <withoff>*Date*: Thu, 15 Oct 1998 00:28:57 -0400*Sender*: owner-wri-mathgroup at wolfram.com

> Dear mathgroup, > > We have just upgraded to release 3 of mathematica and we have found a > problem with the Expand function as described in the mathematica > manual. Here is the mathematica 3.0 output... > > In[3]:= Expand[Cos[x]^3 Sin[x]^2,Trig->True] > > gives > > 3 2 > Out[3]= Cos[x] Sin[x] > > this is not the answer given in the manual, which is... > > Cos[x] - Cos[3 x] - Cos[5 x] > ------ -------- -------- > 8 16 16 I am guessing that you are referring to the manual for Version 2. I didn't see this example in the Version 3 manual, but you can get this behavior in Version 3 using TrigReduce: In[6]:= TrigReduce[Cos[x]^3 Sin[x]^2] //Expand Cos[x] Cos[3 x] Cos[5 x] Out[6]= ------ - -------- - -------- 8 16 16 > We were led to believe that the new version was compatible with the > previous version. > > Is there a switch to obtain compatibility??? There is a listing "Incompatible Changes in Version 3.0" in Appendix A.13 of the Mathematica book, which mentions this change in the Trig option. It is always possible to get Version 2 behavior in Version 3, and most functionality that existed in Version 2 is identical or closely equivalent in Version 3, but there is not a switch that will cause Version 3 to be identical to Version 2 in every respect. > Any comments on this would be appreciated. Also who should I send this > to at Wolfram? You can send technical questions, comments, suggestions, etc., to Wolfram Research technical support at the address support at wolfram.com. Dave Withoff Wolfram Research