Câu hỏi: Cho hàm số $f\left( x \right)=\cos \left( 3x+\dfrac{\pi }{6} \right)$. Trong các khẳng định sau, khẳng định nào đúng?
A. $\int{f\left( x \right)\text{d}x}=3\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
B. $\int{f\left( x \right)\text{d}x}=-\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
C. $\int{f\left( x \right)\text{d}x}=6\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
D. $\int{f\left( x \right)\text{d}x}=\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
A. $\int{f\left( x \right)\text{d}x}=3\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
B. $\int{f\left( x \right)\text{d}x}=-\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
C. $\int{f\left( x \right)\text{d}x}=6\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
D. $\int{f\left( x \right)\text{d}x}=\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$.
$\int{f\left( x \right)\text{d}x}=\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$
Đáp án D.