Đề bài

Cho hàm số $f\left( x \right) = \sin \left( {{x^2}} \right).$ Khi đó, $f'\left( x \right)$ bằng:

A. $2x{\rm{cos}}\left( {{x^2}} \right).$

B. ${\rm{cos}}\left( {{x^2}} \right).$

C. ${x^2}{\rm{cos}}\left( {{x^2}} \right).$

D. $2x{\rm{cos}}\left( {2x} \right).$