convex set的用法和樣例：
例句
- Convex sets and functions have many interesting and useful properties which are not explored in detail here.
凸集和凸函數具有很多重要的和有用的性質，在此不作詳細討論。 - Duality is emphasized throughout,particularly in the form of Fenchel's conjugacy correspondence for convex functions.
這本書的目的是為了提供各類凸集和凸函數理論的介紹，它們在極值問題的應用中發揮核心作用。
