There are 1 questions in this calculation: for each question, the 4 derivative of lC is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ 4th\ derivative\ of\ function\ sech(9223372036854775807)\ with\ respect\ to\ lC：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( sech(9223372036854775807)\right)}{dlC}\\=&-sech(9223372036854775807)tanh(9223372036854775807)*0\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( 0\right)}{dlC}\\=&0\\\\ &\color{blue}{The\ third\ derivative\ of\ function:} \\&\frac{d\left( 0\right)}{dlC}\\=&0\\\\ &\color{blue}{The\ 4th\ derivative\ of\ function:} \\&\frac{d\left( 0\right)}{dlC}\\=&0\\ \end{split}\end{equation} \]

Your problem has not been solved here? Please take a look at the  hot problems ！