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Câu hỏi: Tìm nguyên hàm của hàm $f\left( x \right)=\text{co}{{\text{s}}^{2}}x$
A. $\dfrac{x}{2}-\dfrac{\sin 2x}{4}+C$.
B. $\dfrac{x}{2}-\dfrac{\text{cos}2x}{4}+C$.
C. $\dfrac{x}{2}+\dfrac{\text{cos}2x}{4}+C$.
D. $\dfrac{x}{2}+\dfrac{\sin 2x}{4}+C$.
A. $\dfrac{x}{2}-\dfrac{\sin 2x}{4}+C$.
B. $\dfrac{x}{2}-\dfrac{\text{cos}2x}{4}+C$.
C. $\dfrac{x}{2}+\dfrac{\text{cos}2x}{4}+C$.
D. $\dfrac{x}{2}+\dfrac{\sin 2x}{4}+C$.
Ta có $\int{\text{co}{{\text{s}}^{2}}x\text{d}x=\int{\dfrac{1+\text{cos}2x}{2}}}\text{d}x=\dfrac{x}{2}+\dfrac{1}{4}\sin 2x+C$
Đáp án D.