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Câu hỏi: Tìm nguyên hàm của hàm số $f\left( x \right)=\cos 4x$.
A. $\int{f\left( x \right)\text{d}x}=-\dfrac{1}{4}\sin 4x+C$.
B. $\int{f\left( x \right)\text{d}x}=-4\sin 4x+C$.
C. $\int{f\left( x \right)\text{d}x}=\dfrac{1}{4}\sin 4x+C$.
D. $\int{f\left( x \right)\text{d}x}=4\sin 4x+C$.
A. $\int{f\left( x \right)\text{d}x}=-\dfrac{1}{4}\sin 4x+C$.
B. $\int{f\left( x \right)\text{d}x}=-4\sin 4x+C$.
C. $\int{f\left( x \right)\text{d}x}=\dfrac{1}{4}\sin 4x+C$.
D. $\int{f\left( x \right)\text{d}x}=4\sin 4x+C$.
Ta có: $\int{f\left( x \right)\text{d}x}=\int{\cos 4x \text{d}x=}\dfrac{1}{4}\sin 4x+C$.
Đáp án C.