enow.com Web Search

Search results

1. Results from the WOW.Com Content Network

2. Constructive proof - Wikipedia

   en.wikipedia.org/wiki/Constructive_proof

   Constructive proof. In mathematics, a constructive proof is a method of proof that demonstrates the existence of a mathematical object by creating or providing a method for creating the object. This is in contrast to a non-constructive proof (also known as an existence proof or pure existence theorem), which proves the existence of a particular ...

3. A Guide Book of United States Coins - Wikipedia

   en.wikipedia.org/wiki/A_Guide_Book_of_United...

   A Guide Book of United States Coins (the Red Book) is the longest running price guide for U.S. coins. Across all formats, 24 million copies have been sold. [2] The first edition, dated 1947, went on sale in November 1946. Except for a one-year hiatus in 1950, publication has continued to the present. R. S. Yeoman was the founding compiler of ...

4. United States Proof Set - Wikipedia

   en.wikipedia.org/wiki/United_States_Proof_Set

   United States Proof Set. The United States Mint Proof Set, commonly known as the Proof Set in the United States, is a set of proof coins sold by the United States Mint. The proof set is popular with coin collectors as it is an affordable way to collect examples of United States coinage in proof condition.

5. Intuitionistic logic - Wikipedia

   en.wikipedia.org/wiki/Intuitionistic_logic

   Intuitionistic logic, sometimes more generally called constructive logic, refers to systems of symbolic logic that differ from the systems used for classical logic by more closely mirroring the notion of constructive proof. In particular, systems of intuitionistic logic do not assume the law of the excluded middle and double negation ...

6. Coin grading - Wikipedia

   en.wikipedia.org/wiki/Coin_grading

   Coin grading [1] is the process of determining the grade or condition of a coin, one of the key factors in determining its collectible value. A coin's grade is generally determined by six criteria: strike, preservation, luster, color, attractiveness, and occasionally the country/state in which it was minted. Several grading systems have been ...

7. Proof coinage - Wikipedia

   en.wikipedia.org/wiki/Proof_coinage

   The U.S. had largely stopped striking proof coins in 1916, although a few later specimens exist. From 1936 to 1942, proof coins could be ordered individually from the United States Mint. Beginning in 1950, customers could order proof coins only as complete sets. A 1969 United States Mint Proof set of 5 coins including 40% silver Kennedy half dollar