double trapezium

例句：

1. 1.The double trapezium is a shape that has two parallel sides and one diagonal side.
   双梯形是一种具有两条平行边和一条对角线边的几何形状。
2. 2.In mathematics, the double trapezium can be used to represent the area of a triangle when its base is equal to its height.
   在数学中，双梯形可以用来表示一个三角形的面积，当其底边等于高时。
3. 3. The double trapezium was used as a symbol for the United States in the early 20th century.
   双梯形在20世纪初被用作美国的象征。