证明: $\cos x < \frac{1}{x}$, $\forall\ x\in(0,\frac{\pi}{2})$.
证明: $\cos x < \frac{1}{x}$, $\forall\ x\in(0,\frac{\pi}{2})$.
Answer
证明: $\cos x < \frac{1}{x}$, $\forall\ x\in(0,\frac{\pi}{2})$.