解:用計(jì)算器計(jì)算得,$\pi\approx3.142,$$\sqrt{5}\approx2.236,$$\sqrt{7}\approx2.646,$則$\vert\sqrt{5}-\sqrt{7}\vert=\sqrt{7}-\sqrt{5}\approx2.646 - 2.236=0.41,$所以$\frac{\pi}{2}-\vert\sqrt{5}-\sqrt{7}\vert+\frac{2}{3}\approx\frac{3.142}{2}-0.41 + 0.667\approx1.571 - 0.41 + 0.667=1.161 + 0.667=1.828\approx1.83$