# Plot an infinite sum

I want to plot the following equation (w-$$\delta$$ graph)

Ty Tx and ly are constant and I will assign a value for them. I am a new one on the Mathematica and can not handle this.

• It seems that this sum cannot be found symbolically, however there is numerical sum NSum which can be computed with numerical values of constants e.g. With[{Tx = 0.6, Ty = 0.93}, NSum[(-1)^( n - 1)/(2 n - 1)^3 (1 - 1/ Cosh[(2 n - 1) Pi/(2 Tx) Sqrt[Ty/Tx]]), {n, 1, Infinity}]] Mar 2 '20 at 14:09
• Thank you. I also tried Sum[f,{n, 1, Infinity, 2}] and think it works pretty well. Mar 3 '20 at 12:26