There are 1 questions in this calculation: for each question, the 1 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ first\ derivative\ of\ function\ \frac{0.81mg}{(sin(x) + 0.81cos(x))}\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = \frac{0.81mg}{(sin(x) + 0.81cos(x))}\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( \frac{0.81mg}{(sin(x) + 0.81cos(x))}\right)}{dx}\\=&0.81(\frac{-(cos(x) + 0.81*-sin(x))}{(sin(x) + 0.81cos(x))^{2}})mg + 0\\=&\frac{-0.81mgcos(x)}{(sin(x) + 0.81cos(x))(sin(x) + 0.81cos(x))} + \frac{0.6561mgsin(x)}{(sin(x) + 0.81cos(x))(sin(x) + 0.81cos(x))}\\ \end{split}\end{equation} \]

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