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Câu hỏi: Cho hàm số $f\left( x \right)=3-2{{\cos }^{2}}x$. Khẳng định nào dưới đây đúng?
A. $\int{f\left( x \right)\text{d}x}=2x+\sin 2x+C$.
B. $\int{f\left( x \right)\text{d}x}=2x-\dfrac{1}{2}\sin 2x+C$.
C. $\int{f\left( x \right)\text{d}x}=2\sin 2x+C$.
D. $\int{f\left( x \right)\text{d}x}=2x+\dfrac{1}{2}\sin 2x+C$.
A. $\int{f\left( x \right)\text{d}x}=2x+\sin 2x+C$.
B. $\int{f\left( x \right)\text{d}x}=2x-\dfrac{1}{2}\sin 2x+C$.
C. $\int{f\left( x \right)\text{d}x}=2\sin 2x+C$.
D. $\int{f\left( x \right)\text{d}x}=2x+\dfrac{1}{2}\sin 2x+C$.
Ta có: $\int{f\left( x \right)\text{d}x}=\int{\left( 3-2{{\cos }^{2}}x \right)\text{d}x}=\int{\left( 2-\cos 2x \right)\text{d}x}=2x-\dfrac{1}{2}\sin 2x+C$.
Đáp án B.