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Câu hỏi: Tích phân $\int\limits_{0}^{\dfrac{\pi }{15}}{\cos 5xdx}$ bằng
A. $-\dfrac{\sqrt{3}}{10}.$
B. $\dfrac{\sqrt{3}}{10}.$
C. $\dfrac{\sqrt{3}-1}{2}.$
D. $\dfrac{\sqrt{3}+1}{2}.$
A. $-\dfrac{\sqrt{3}}{10}.$
B. $\dfrac{\sqrt{3}}{10}.$
C. $\dfrac{\sqrt{3}-1}{2}.$
D. $\dfrac{\sqrt{3}+1}{2}.$
Ta có $\int\limits_{0}^{\dfrac{\pi }{15}}{\cos 5xdx}=\left. \dfrac{\sin 5x}{5} \right|_{0}^{\dfrac{\pi }{15}}=\dfrac{\sqrt{3}}{10}$.
Đáp án B.