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This shows that non-constructive proofs can have constructive outcomes. [1] The main idea is that a problem can be solved using an algorithm that uses, as a parameter, an unknown set. Although the set is unknown, we know that it must be finite, and thus a polynomial-time algorithm exists.
A non-constructive proof might show a solution exists without specifying either an algorithm to obtain it or a specific bound. Even if the proof is constructive, showing an explicit bounding polynomial and algorithmic details, if the polynomial is not very low-order the algorithm might not be sufficiently efficient in practice.
Algorithms from P to NP, volume 1 - Design and Efficiency. Redwood City, California: Benjamin/Cummings Publishing Company, Inc. Discusses intractability of problems with algorithms having exponential performance in Chapter 2, "Mathematical techniques for the analysis of algorithms." Weinberger, Shmuel (2005). Computers, rigidity, and moduli ...
Yet another major class is the dynamic problems, in which the goal is to find an efficient algorithm for finding a solution repeatedly after each incremental modification of the input data (addition or deletion input geometric elements). Algorithms for problems of this type typically involve dynamic data structures. Any of the computational ...
From the other direction, there has been considerable clarification of what constructive mathematics is—without the emergence of a 'master theory'. For example, according to Errett Bishop's definitions, the continuity of a function such as sin(x) should be proved as a constructive bound on the modulus of continuity, meaning that the existential content of the assertion of continuity is a ...
triangles bounded by a finite line segment and by two parallel rays that meet at a vertex on the line at infinity. For instance, an arrangement of five finite lines forming a pentagram, together with a sixth line at infinity, has ten triangles: five in the pentagram, and five more bounded by pairs of rays.
See examples in the table at the right. Note that the degree is the same if we count switches from 2 to 3 minus 3 to 2, or from 3 to 1 minus 1 to 3. Musin proved that the number of fully labeled triangles is at least the degree of the labeling. [20] In particular, if the degree is nonzero, then there exists at least one fully labeled triangle.
The square root of 2 is equal to the length of the hypotenuse of a right triangle with legs of length 1 and is therefore a constructible number. In geometry and algebra, a real number is constructible if and only if, given a line segment of unit length, a line segment of length | | can be constructed with compass and straightedge in a finite number of steps.