Cho hàm số f(x) = 2x - 4 khi x lớn hơn hoặc bằng 4 1/ 4 x^3 - x^2

Câu hỏi :

Cho hàm số $f\left(x\right)=\left\{\begin{array}{l}2x-4\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}khi\hspace{0.17em}}x\ge 4\\ \frac{1}{4}{x}^3-x^2+x\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}khi\hspace{0.17em}}x<4\end{array}\right.$. Tích phân $\underset{0}{\overset{\frac{\pi }{2}}{\int }}f\left(2{\sin }^{2}x+3\right)\sin 2x\text{d}x$ bằng