Integration Problems

*To*: mathgroup at smc.vnet.net*Subject*: [mg13926] Integration Problems*From*: Georgios Kotsalis <kotsalis at mit.edu>*Date*: Mon, 7 Sep 1998 01:22:51 -0400*Organization*: Massachusetts Institute of Technology*Sender*: owner-wri-mathgroup at wolfram.com

Dear Sirs , while performing the following evaluation, i received an unexpected result: 1.) W1[x_,t_]:= q[2,1][t] (Sin[4.73 x] - Cos[4.73 x] + Exp[-4.73 x] + Exp[-4.73 (1-x)]); 2.) W2[x_,t_]:=Evaluate[(D[W1[x,t],{x,2} ])^2] 3.) Integrate[W2[x,t],{x,0,1}] Answer: (509.399 -2.922295 X 10^-5 I) q[2,1][t]^2 Could you please tell me, why does an imaginary part arise though the function that is being integrated is real ? Thank you very much for your time. Georgios