题目

When you enter a supermarket, you see shelves full of food. You walk between the shelves. You carry a shopping basket and your food is in it.You probably hear soft, slow music as you walk between the shelves. If you hear fast music, you walk quickly. The supermarket plays slow music. You walk slowly and have more time to buy things.Maybe you go to the meat department first. There is some meat on sale, and you want to find it. The manager of the supermarket knows where customers enter the meat department. The cheaper meat is at the other end of the meat department, away from where the customers（2001•安徽）如图所示，花园边墙上有一宽为1m的矩形门ABCD，量得门框对角线AC的长为2m．现准备打掉部分墙体，使其变为以AC为直径的圆弧形门，问要打掉墙体的面积是多少？（精确到0.1m2，π≈3.14，≈1.73）