Câu hỏi: Nếu $\int{f\left( x \right)\text{d}x}={{e}^{x}}+\sin x+C$ thì $f\left( x \right)$ bằng. A. ${{e}^{x}}-\cos x$. B. ${{e}^{x}}+\sin x$. C. ${{e}^{x}}-\sin x$. D. ${{e}^{x}}+\cos x$.
Ta có: $f\left( x \right)={{\left( {{e}^{x}}+\sin x+C \right)}^{\prime }}={{e}^{x}}+\cos x$.