Cho \(\int\limits_{0}^{\frac{\pi }{2}}{f\left( x \right)\text{d}x}=5\). Tính \(I=\int\limits_{0}^{\frac{\pi }{2}}{\left[ f\left( x \right)+2\sin x \right]\text{d}x}\).

* Hướng dẫn giải

\(I = \int\limits_0^{\frac{\pi }{2}} {\left[ {f\left( x \right)\, + 2\sin x} \right]\,{\rm{d}}x = \int\limits_0^{\frac{\pi }{2}} {f\left( x \right)\,{\rm{d}}x\,{\rm{ + 2}}\int\limits_0^{{\textstyle{\pi  \over 2}}} {\sin x\,{\rm{d}}x} } } \)

\( = \int\limits_0^{\frac{\pi }{2}} {f\left( x \right)} \,{\rm{d}}x\,\, - \left. {2\cos x} \right|_0^{\frac{\pi }{2}} = 5 - 2\left( {0 - 1} \right) = 7\)