七巧板起源于我国唐宋时代。最早称作“燕几图”.19世纪初,七巧板流传到西方。被称为“东方魔板”(如图1).它成为中华民族智慧的一个代表,得到了全世界的赞誉.七巧板仅由七块组成。即五个等腰直角三角形、一个正方形和一个平行四边形.但用它可以拼出多种多样的图形.近年来,全国各省、市的中考、竞赛题出现以七巧板为背景的一些有关面积计算问题.现举例说明. 例1(2002年山东济南市中考题改编)如图1,用一块边长为2的正方形厚纸板,做了一套七巧板,沿画出的线剪开.现用它拼出一座桥(如图2),这座桥的阴影部分的面积是( )A.4;B.3;C.2;D.1.解析:仔细观察会发现:阴影部分的面积占大正方形面积的1/2, Tangrams originated from the Tang and Song dynasties in China. The earliest known as the “Yanjitu”. In the early 19th century, Tangrams spread to the West. It is called “Oriental Magic Board” (Figure 1). It has become a representative of the wisdom of the Chinese nation and has received praise from all over the world. The jigsaw puzzle consists of only seven pieces. That is, five isosceles right triangles, one square, and one parallelogram. But it can be used to spell a variety of graphics. In recent years, there have been some issues related to area calculation with the tangram as the background for the examinations and competitions in provinces and cities across the country. Here is an example. Example 1 (Adapted from the examination question in Jinan City, Shandong Province, 2002) As shown in Figure 1, a piece of jigsaw puzzle was made from a square cardboard with a side length of 2, cut along the drawn line. In a bridge (Figure 2), the area of ​​the shadowed part of the bridge is () A.4; B.3; C.2; D.1. Analysis: If you look closely, you will find that the shadow area covers a large square. 1/2 of the area,