There are 1 questions in this calculation: for each question, the 2 derivative of z is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ second\ derivative\ of\ function\ \frac{z}{sin(z)}\ with\ respect\ to\ z：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( \frac{z}{sin(z)}\right)}{dz}\\=&\frac{1}{sin(z)} + \frac{z*-cos(z)}{sin^{2}(z)}\\=&\frac{1}{sin(z)} - \frac{zcos(z)}{sin^{2}(z)}\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( \frac{1}{sin(z)} - \frac{zcos(z)}{sin^{2}(z)}\right)}{dz}\\=&\frac{-cos(z)}{sin^{2}(z)} - \frac{cos(z)}{sin^{2}(z)} - \frac{z*-2cos(z)cos(z)}{sin^{3}(z)} - \frac{z*-sin(z)}{sin^{2}(z)}\\=&\frac{-2cos(z)}{sin^{2}(z)} + \frac{2zcos^{2}(z)}{sin^{3}(z)} + \frac{z}{sin(z)}\\ \end{split}\end{equation} \]

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