zhèng míng liǎng gè tú xíng zhī jiān cún zài bǎo cháng duì yìng shì yán jiū tú xíng quán děng de guān jiàn bù zhòu

证明两个图形之间存在保长对应，是研究图形全等的关键步骤。

Proving that an isometry exists between two figures is a key step in studying figure congruence.