There are 1 questions in this calculation: for each question, the 4 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ 4th\ derivative\ of\ function\ cos(i)nx\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = nxcos(i)\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( nxcos(i)\right)}{dx}\\=&ncos(i) + nx*-sin(i)*0\\=&ncos(i)\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( ncos(i)\right)}{dx}\\=&n*-sin(i)*0\\\\ &\color{blue}{The\ third\ derivative\ of\ function:} \\&\frac{d\left( 0\right)}{dx}\\=&0\\\\ &\color{blue}{The\ 4th\ derivative\ of\ function:} \\&\frac{d\left( 0\right)}{dx}\\=&0\\ \end{split}\end{equation} \]

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