MATLAB: Is there any one who can help me how to sum the following summation expression? I tried but it said to many inputs. Thank you for your help!

infinite summation of functions.Symbolic Math Toolbox

U(x,y) = ∑[∝.ϕ1(x) + β.ϕ2(x)].ψ(y), the summation is k : 0 --> infinity. 
Where    ψ(y)=sin(kπy), b=√(1/(2ϵ)^2 +(kπ)^2 ), 
           ϕ1(x)=e^(x/(2ϵ)) (sinh(b.(1-x)))/(sinh(b)), 
           ϕ2(x)=e^((x-1)/(2ϵ)).(sinh(b.x)/(sinh(b)), 
           ∝=2/kπ (cos(0.45kπ) ), 
           β=∝.(b.e^(1/(2ϵ))/(sinh(b))⁄(1/2ϵ+b.(cosh(b)/sinh(b)))

Best Answer

The first result with ‘symsum’ very likely indicates that ‘symsum’ is unable to compute this particular infinite sum.
The second result indicating too many input arguments refers to the ‘sum’ function. See:
   http://www.mathworks.com/help/matlab/ref/sum.html
The ‘sum’ function is not symbolic but is numeric instead, and the arguments you gave, namely k,1,Inf, are inappropriate. You need to make ‘k’ a vector and unfortunately it has to be of finite length so you can only approximate an infinite sum with this method.
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