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

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