trapezoidal pulse

例句：

1. 1.The shape of the trapezoid is a key to understanding its properties.
   梯形的形状是理解其属性的关键。
2. 2. The trapezoid was used in ancient times as a tool for measuring lengths.
   梯形在古代被用作测量长度的工具。
3. 3. The trapezoid's vertices are where the two parallel sides meet.
   梯形的两个平行边相交的地方是顶点。