Question

Tích phân \(\int\limits^{\dfrac{\pi}{5}}_{\dfrac{\pi}{7}}\sin xdx\) có giá trị bằng:

A. \(\sin\dfrac{\pi}{5}-\sin\dfrac{\pi}{7}.\).                    B. \(\sin\dfrac{\pi}{7}-\sin\dfrac{\pi}{5}.\).               

C. \(\cos\dfrac{\pi}{5}-\cos\dfrac{\pi}{7}.\).                   D. \(\cos\dfrac{\pi}{7}-\cos\dfrac{\pi}{5}.\).

Answer 1

\(\int\limits_{\frac{\pi }{7}}^{\frac{\pi }{5}} {\sin xdx} = \left. { - \cos x} \right|_{\frac{\pi }{7}}^{\frac{\pi }{5}} = \cos \frac{\pi }{7} - \cos \frac{\pi }{5}\)

Chọn D