\int_{0}^{\frac{\pi}{2}}\frac{\sin x}{\sqrt{1+2\cos x}}dx \\\\ \text{Let} \,\, y=1+2\cos x \\\\ \frac{dy}{dx}=-2\sin x \Rightarrow dx=-\frac{dy}{2\sin x} \\\\ \text{When} \,\, x=\frac{\pi}{2}, \,\, y=1 \\\\ \text{When} \,\, x=0, \,\, y=3 \\\\ \therefore \int_{0}^{\frac{\pi}{2}}\frac{\sin...