RE:Beginner--getting rid of dot products with zero

*To*: mathgroup at smc.vnet.net*Subject*: [mg66882] RE:Beginner--getting rid of dot products with zero*From*: smanky at gmx.de*Date*: Fri, 2 Jun 2006 04:09:25 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

sorry that my question was apparently not clear. i have no problem with computing the derivatives. the expressions with Total[] etc all make sense. however, the derivatives include ugly terms that are simply zero. there are terms of the following form 0.{exp, exp, exp} or {exp, exp, exp}.0 in both cases the whole thing is zero and they should drop out... i am surprised that mathematica is not getting rid of them by itself, or at least when i use Simplify[]. so i am looking for a clever way to tell mathematica that it should disregard those terms. thanks, ~s p.s. if it is still not clear, or you just want to see for yourself, run: finish = 2; i = Table[i, {i, finish}]; d1[k1_, k2_] = Exp[k1*i + k2*i^2]; d2[k1_, k2_] = Total[Exp[k1*i + k2*i^2]]; w[k1_, k2_, i] = d1[k1, k2]/d2[k1, k2]; q[k1_, k2_] = x.w[k1, k2, i]; L[k1_, k2_, alpha_, beta_ ] = Total[Log[q[k1, k2]]] + Total[(y - alpha - beta*q[k1, k2])^2/q[k1, k2]]; \!\(Simplify[∂\_beta\ L[k1, \ k2, \ alpha, \ beta]]\) Link to the forum page for this post: http://www.mathematica-users.org/webMathematica/wiki/wiki.jsp?pageName=Special:Forum_ViewTopic&pid=10811#p10811 Posted through http://www.mathematica-users.org [[postId=10811]]