There are 1 questions in this calculation: for each question, the 3 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ third\ derivative\ of\ function\ {e}^{x}cos(x)\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( {e}^{x}cos(x)\right)}{dx}\\=&({e}^{x}((1)ln(e) + \frac{(x)(0)}{(e)}))cos(x) + {e}^{x}*-sin(x)\\=&{e}^{x}cos(x) - {e}^{x}sin(x)\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( {e}^{x}cos(x) - {e}^{x}sin(x)\right)}{dx}\\=&({e}^{x}((1)ln(e) + \frac{(x)(0)}{(e)}))cos(x) + {e}^{x}*-sin(x) - ({e}^{x}((1)ln(e) + \frac{(x)(0)}{(e)}))sin(x) - {e}^{x}cos(x)\\=&-2{e}^{x}sin(x)\\\\ &\color{blue}{The\ third\ derivative\ of\ function:} \\&\frac{d\left( -2{e}^{x}sin(x)\right)}{dx}\\=&-2({e}^{x}((1)ln(e) + \frac{(x)(0)}{(e)}))sin(x) - 2{e}^{x}cos(x)\\=&-2{e}^{x}sin(x) - 2{e}^{x}cos(x)\\ \end{split}\end{equation} \]

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