Tìm nguyên hàm \(F\left( x \right) = \int {{\mathop{\rm s}\nolimits} {\rm{i}}{{\rm{n}}^2}{\rm{2}}x{\rm{d}}x} \).

A. \(F\left( x \right) = \frac{1}{2}x - \frac{1}{8}\sin 4x + C\)

B. \(F\left( x \right) = \frac{1}{2}x + \frac{1}{8}\sin 4x + C\)

C. \(F\left( x \right) = \frac{1}{2}x - \frac{1}{8}\sin 4x\)

D. \(F\left( x \right) = \frac{1}{2}x - \frac{1}{8}{\rm{cos}}4x + C\)