1. One of the key concepts in logic is the notion of coextension, which refers to the relationship between two sets that have the same members.
逻辑学中的一个关键概念是共拓，它指的是拥有相同成员的两个集合之间的关系。

2. The coextension of happiness and success is often assumed, but not always true.
幸福和成功的共同存在常常被认为是事实，但并非总是真实的。

3. The coextension of these two principles will guide us in making ethical decisions.
这两个原则的共同行为将指导我们做出伦理决策。