安裝 Steam
登入
|
語言
簡體中文
日本語(日文)
한국어(韓文)
ไทย(泰文)
Български(保加利亞文)
Čeština(捷克文)
Dansk(丹麥文)
Deutsch(德文)
English(英文)
Español - España(西班牙文 - 西班牙)
Español - Latinoamérica(西班牙文 - 拉丁美洲)
Ελληνικά(希臘文)
Français(法文)
Italiano(義大利文)
Bahasa Indonesia(印尼語)
Magyar(匈牙利文)
Nederlands(荷蘭文)
Norsk(挪威文)
Polski(波蘭文)
Português(葡萄牙文 - 葡萄牙)
Português - Brasil(葡萄牙文 - 巴西)
Română(羅馬尼亞文)
Русский(俄文)
Suomi(芬蘭文)
Svenska(瑞典文)
Türkçe(土耳其文)
tiếng Việt(越南文)
Українська(烏克蘭文)
回報翻譯問題
/)─―ヘ
_/ \
/ ● ●丶
| ▼ |
| 亠ノ
U ̄U ̄ ̄ ̄ ̄U ̄
+rep
.
The ⊢ symbol has not changed; it means that the formula to which it applies is asserted to be true. ⊃ is logical implication, and ≡ is logical equivalence. Λ is the empty set, which we write nowadays as ∅. ∩ ∪ and ∈ have their modern meanings: ∩ and ∪ are the set intersection and the union operators, and x∈y means that x is an element of set y.
The remaining points are semantic. α and β are sets. 1 denotes the set of all sets that have exactly one element. That is, it's the set { c : there exists a such that c = { a } }. Theorems about 1 include, for example:
that Λ∉1 (∗52.21),
that if α∈1 then there is some x such that α = {x} (∗52.1), and
that {x}∈1 (∗52.22).
2 is similarly the set of all sets that have exactly two elements. An important theorem about 2 is ∗54.3, which says
∗54.3.⊢2=α^{(∃x).x∈α.α−ι‘x∈1}.