There are 1 questions in this calculation: for each question, the 2 derivative of x is calculated.
    Note that variables are case sensitive.
\[ \begin{equation}\begin{split}[1/1]Find\ the\ second\ derivative\ of\ function\ a(cos(bx) + \frac{ccos(2bx)}{4})\ with\ respect\ to\ x：\\\end{split}\end{equation} \]\[ \begin{equation}\begin{split}\\Solution:&\\ &Primitive\ function\ = acos(bx) + \frac{1}{4}accos(2bx)\\&\color{blue}{The\ first\ derivative\ function：}\\&\frac{d\left( acos(bx) + \frac{1}{4}accos(2bx)\right)}{dx}\\=&a*-sin(bx)b + \frac{1}{4}ac*-sin(2bx)*2b\\=&-absin(bx) - \frac{abcsin(2bx)}{2}\\\\ &\color{blue}{The\ second\ derivative\ of\ function:} \\&\frac{d\left( -absin(bx) - \frac{abcsin(2bx)}{2}\right)}{dx}\\=&-abcos(bx)b - \frac{abccos(2bx)*2b}{2}\\=&-ab^{2}cos(bx) - ab^{2}ccos(2bx)\\ \end{split}\end{equation} \]

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