Search results
Results from the WOW.Com Content Network
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 ...
Proof coinage refers to special early samples of a coin issue, historically made for checking the dies (as in demonstrating that something is true) and for archival purposes. In modern times, proofs are often struck in greater numbers, especially for coin collectors (numismatists). [1] Nearly all countries have issued proof coinage.
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 ...
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.
In contrast, a constructive proof establishes that a particular object exists by providing a method of finding it. The following famous example of a nonconstructive proof shows that there exist two irrational numbers a and b such that a b {\displaystyle a^{b}} is a rational number .
However, there is a non-constructive proof that shows that linkedness is decidable in polynomial time. The proof relies on the following facts: The set of graphs for which the answer is "yes" is closed under taking minors. I. e., if a graph G can be embedded linklessly in 3-d space, then every minor of G can also be embedded linklessly.
Cameo finish. A standard uncirculated Lincoln cent. A Lincoln cent displaying deep cameo. In coin grading, cameo is the amount of contrast between the relief (raised or recessed design) and field (background). Cameo is usually seen on proof coinage, with the relief featuring a frosted finish and the field being mirror-like. [1]
Minimal logic, or minimal calculus, is a symbolic logic system originally developed by Ingebrigt Johansson. [1] It is an intuitionistic and paraconsistent logic, that rejects both the law of the excluded middle as well as the principle of explosion (ex falso quodlibet), and therefore holding neither of the following two derivations as valid: