@Carl Love

Thank you for your reply. I understand now. Actually,  yes the symbols in the scalar part will eventually have vector and matrices substituted for them. 

Thank you ^^ 

@vv 5868

Okay, I understand now ... . But unfortunately, I can not find a guide of Maple that explains with details the use of the subsop function. So the choice of 2=s means what the second part of expression replaced by s ?? because when I change the value of M to 3 instead of 2, the Maple can not evaluate the integral. Do you have any explanation of that? and why did you use the undefined integral as the solution? 

@vv 5686 thank you very much for replying. I am not sure that I understand the first line. In my code, I iterate ( fun ij ) in order of i and j value so what do you mean by fun11[1] ???. And for the second line do you mean that you replace the s by the value 2 ?? 

Thank you, sir, for your help.