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Proofs by contradiction - Vocabulary

Vocabulary on Induction proofs

  • Base Case: The initial step of an induction proof, demonstrating that the statement holds for the first value.
  • Conclusion: The final part of the induction proof, restating that the statement holds for all intended values (initially defined by the exercise).
  • Conjecture: A mathematical statement which appears to be true, but has not been formally proven. A conjecture can be thought of as the mathematicians way of saying “I believe that this is true, but I have no proof yet”. A conjecture is a good guess or an idea about a pattern.
  • Hypothesis (Inductive hypothesis): The assumption made during the inductive step, assuming the statement is true for some arbitrary case.
  • Induction Principle: The logical principle allowing conclusions about infinite sets by establishing a base case and an inductive step.
  • Inductive Step: The part of an induction proof where the truth of the statement for the next case is demonstrated based on the inductive hypothesis.
  • Inequality: A mathematical relation used frequently in induction to demonstrate the validity of a statement through comparison.
  • Integers: Represented by Z\mathbb{Z}Z, the set of integers includes all positive and negative whole numbers, including zero. Mathematically, they are defined as Z={…,−1,0,1,2,…}\displaystyle \mathbb{Z} = \left\{\ldots,-1, 0, 1, 2, \ldots \right\}Z={…,−1,0,1,2,…}.
  • Natural Numbers: The most typical set over which induction proofs are performed, denoted by N\mathbb{N}N. The set of natural numbers (according to the IB standard) are N={0,1,2,…}\mathbb{N} = \left\{ 0, 1, 2, \ldots \right\}N={0,1,2,…} (however typically the set of natural numbers does not include zero).
  • Proof by Mathematical Induction: A structured method for proving a mathematical statement holds true for all integers greater than or equal to a certain initial integer.
  • Proposition: A statement that is either true or false. For example “Portugal is in Europe” is a true statement and “All primes are odd numbers” is a false statement. We use P(n)P(n)P(n) ("P of n") to denote a propositional function (a formula which becomes true or false if you plug in a value for nnn).
  • Recursive Relation: A formula or relation in induction that defines each term based on preceding terms.
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