Problem with singularities in Plot3D

*To*: mathgroup at smc.vnet.net*Subject*: [mg55322] Problem with singularities in Plot3D*From*: "Steeve Brechmann \(schumi\)" <steevebrechmann at yahoo.ca>*Date*: Sat, 19 Mar 2005 04:45:28 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I have a little problem with the Plot3D command of Mathematica. I want to plot the 3D graphics of : eqt[q_,N_,M_]:= - (3*q/(8*Pi))*(Sum[(Cos[4*Pi*n*d]/(2*n*d))-(Sin[4*Pi*n*d]/(8*Pi*(n*d)^2))-(Cos[4*Pi*n*d]/(32*Pi^2*(n*d)^3)),{n,1,N}] - Sum[(Cos[4*Pi*Abs[z0-m*d]]/Abs[z0-m*d])-(Sin[4*Pi*Abs[z0-m*d]]/(4*Pi*Abs[z0-m*d]^2))-(Cos[4*Pi*Abs[z0-m*d]]/(16*Pi^2*Abs[z0-m*d]^3)),{m,-M,M}]) Plot3D[Evaluate[eqt[1,10,10]],{z0,0,3},{d,0.1,6},PlotPoints->50]; Like you see, my expression eqt[q,N,M] have some singularities at d = 0 and Abs[z0-m*d] = 0. How can i say to Mathematica that it must ignore the singularities Abs[z0-m*d] = 0 ? Thanks for your help. Steeve Brechmann von Brechenmacher Physics Department, Laval University steevebrechmann at yahoo.ca