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