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