tính tích phân cos (x/2)^2 dx bằng:

15/40

\[\int {{{\left( {\cos \frac{x}{2}} \right)}^2}{\rm{d}}x} \] bằng:

\[x + \sin x + C\].

\[\frac{1}{3}{\left( {\cos \frac{x}{2}} \right)^3} + C\].

\[{\left( {\sin \frac{x}{2}} \right)^2} + C\].

\[\frac{1}{2}x + \frac{1}{2}\sin x + C\].

Giải thích

Chọn D

Ta có: \[\int {{{\left( {\cos \frac{x}{2}} \right)}^2}{\rm{d}}x} = \int {\frac{{1 + \cos x}}{2}{\rm{d}}x} = \frac{1}{2}\int {{\rm{d}}x} + \frac{1}{2}\int {\cos x{\rm{d}}x} = \frac{1}{2}x + \frac{1}{2}\sin x + C\].