There are 1 questions in this calculation: for each question, the 2 derivative of T is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ second\ derivative\ of\ function\ n(kT)ln(({(2cosh(\frac{j}{(kT)}))}^{N}))\ with\ respect\ to\ T：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = nkTln((2cosh(\frac{j}{kT}))^{N})\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( nkTln((2cosh(\frac{j}{kT}))^{N})\right)}{dT}\\=&nkln((2cosh(\frac{j}{kT}))^{N}) + \frac{nkT((2cosh(\frac{j}{kT}))^{N}((0)ln(2cosh(\frac{j}{kT})) + \frac{(N)(\frac{2sinh(\frac{j}{kT})j*-1}{kT^{2}})}{(2cosh(\frac{j}{kT}))}))}{((2cosh(\frac{j}{kT}))^{N})}\\=&nkln((2cosh(\frac{j}{kT}))^{N}) - \frac{njNsinh(\frac{j}{kT})}{Tcosh(\frac{j}{kT})}\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( nkln((2cosh(\frac{j}{kT}))^{N}) - \frac{njNsinh(\frac{j}{kT})}{Tcosh(\frac{j}{kT})}\right)}{dT}\\=&\frac{nk((2cosh(\frac{j}{kT}))^{N}((0)ln(2cosh(\frac{j}{kT})) + \frac{(N)(\frac{2sinh(\frac{j}{kT})j*-1}{kT^{2}})}{(2cosh(\frac{j}{kT}))}))}{((2cosh(\frac{j}{kT}))^{N})} - \frac{njN*-sinh(\frac{j}{kT})}{T^{2}cosh(\frac{j}{kT})} - \frac{njNcosh(\frac{j}{kT})j*-1}{TkT^{2}cosh(\frac{j}{kT})} - \frac{njNsinh(\frac{j}{kT})*-sinh(\frac{j}{kT})j*-1}{Tcosh^{2}(\frac{j}{kT})kT^{2}}\\=& - \frac{nj^{2}Nsinh^{2}(\frac{j}{kT})}{kT^{3}cosh^{2}(\frac{j}{kT})} + \frac{nj^{2}N}{kT^{3}}\\ \end{split}\end{equation} \]

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