概述我们曾经探索过平行四边形、菱形、矩形、正方形和梯形的性质及特征.那时是采用平移、对称及旋转等手段直观地获得了这些图形的有关知识.现在我们将用公理和已有的定理来证明这些图形的性质和特征.这不仅加深了我们对这些图形的认识,而且使我们的认识从直观升到理性的高度. Overview We have explored the nature and characteristics of parallelograms, diamonds, rectangles, squares, and trapezoids. At that time, the knowledge of these graphs was intuitively obtained by means of translation, symmetry, and rotation. Now we will use axioms and existing ones. Theorem to prove the nature and characteristics of these graphics. This not only deepens our understanding of these graphics, but also makes our understanding from the intuitive to the height of reason.