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Câu hỏi: Tìm nguyên hàm của hàm số $f(x)=\cos \left( 3x+\dfrac{\pi }{6} \right)$.
A. $\int{f(x)dx=\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
B. $\int{f(x).dx=\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
C. $\int{f(x)dx=-\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
D. $\int{f(x)dx=\dfrac{1}{6}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
A. $\int{f(x)dx=\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
B. $\int{f(x).dx=\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
C. $\int{f(x)dx=-\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
D. $\int{f(x)dx=\dfrac{1}{6}\sin \left( 3x+\dfrac{\pi }{6} \right)+C}$.
$\int{f(x)dx=\dfrac{1}{3}\int{\cos \left( 3x+\dfrac{\pi }{6} \right)d\left( 3x+\dfrac{\pi }{6} \right)=}}\dfrac{1}{3}\sin \left( 3x+\dfrac{\pi }{6} \right)+C$
Đáp án A.