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

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