Mathematical induction is a concept in mathematics that is used to prove various mathematical statements and theorems. The principle of mathematical induction is sometimes referred to as PMI. It is a technique that is used to prove the basic theorems in mathematics which involve the solution up to n finite natural terms.
The principle of Mathematical Induction is widely used in proving various statements such as a sum of first n natural numbers is given by the formula n(n+1)/2. This can be easily proved using the Principle of Mathematical Induction. In this article, we will learn about the principle of mathematical induction, its statement, its example, and others in detail.
Mathematical Induction is one of the fundamental methods of writing proofs and it is used to prove a given statement about any well-organized set. Generally, it is used for proving results or establishing statements that are formulated in terms of n, where n is a natural number. Suppose P(n) is a statement for n natural number then it can be proved using the Principle of Mathematical Induction, Firstly we will prove for P(1) then let P(k) is true then prove for P(k+1). If P(k+1) holds true then we say that P(n) is true by the principle of mathematical induction.
We can compare mathematical induction to falling dominoes. When a domino falls, it knocks down the next domino in succession. The first domino knocks down the second one, the second one knocks down the third, and so on. In the end, all of the dominoes will be bowled over. But there are some conditions to be fulfilled:
The method can be extended to prove statements about more general well-founded structures, such as trees; this generalization, known as structural induction, is used in mathematical logic and computer science. Mathematical induction in this extended sense is closely related to recursion. Mathematical induction is an inference rule used in formal proofs, and is the foundation of most correctness proofs for computer programs.[3]
Although its name may suggest otherwise, mathematical induction should not be confused with inductive reasoning as used in philosophy (see Problem of induction). The mathematical method examines infinitely many cases to prove a general statement, but does so by a finite chain of deductive reasoning involving the variable n \displaystyle n , which can take infinitely many values.[4]
The earliest implicit proof by mathematical induction was written by al-Karaji around 1000 AD, who applied it to arithmetic sequences to prove the binomial theorem and properties of Pascal's triangle. Whilst the original work was lost, it was later referenced by Al-Samawal al-Maghribi in his treatise al-Bahir fi'l-jabr (The Brilliant in Algebra) in around 1150 AD.[6][7]
The induction hypothesis was also employed by the Swiss Jakob Bernoulli, and from then on it became well known. The modern formal treatment of the principle came only in the 19th century, with George Boole,[13] Augustus De Morgan, Charles Sanders Peirce,[14][15] Giuseppe Peano, and Richard Dedekind.[9]
The method of infinite descent is a variation of mathematical induction which was used by Pierre de Fermat. It is used to show that some statement Q(n) is false for all natural numbers n. Its traditional form consists of showing that if Q(n) is true for some natural number n, it also holds for some strictly smaller natural number m. Because there are no infinite decreasing sequences of natural numbers, this situation would be impossible, thereby showing (by contradiction) that Q(n) cannot be true for any n.
The validity of this method can be verified from the usual principle of mathematical induction. Using mathematical induction on the statement P(n) defined as "Q(m) is false for all natural numbers m less than or equal to n", it follows that P(n) holds for all n, which means that Q(n) is false for every natural number n.
whereupon the induction principle "automates" n applications of this step in getting from P(0) to P(n). This could be called "predecessor induction" because each step proves something about a number from something about that number's predecessor.
The induction step must be proved for all values of n. To illustrate this, Joel E. Cohen proposed the following argument, which purports to prove by mathematical induction that all horses are of the same color:[23]
One variation of the principle of complete induction can be generalized for statements about elements of any well-founded set, that is, a set with an irreflexive relation < that contains no infinite descending chains. Every set representing an ordinal number is well-founded, the set of natural numbers is one of them.
The principle of mathematical induction is usually stated as an axiom of the natural numbers; see Peano axioms. It is strictly stronger than the well-ordering principle in the context of the other Peano axioms. Suppose the following:
Peano's axioms with the induction principle uniquely model the natural numbers. Replacing the induction principle with the well-ordering principle allows for more exotic models that fulfill all the axioms.[24]
It is mistakenly printed in several books[24] and sources that the well-ordering principle is equivalent to the induction axiom. In the context of the other Peano axioms, this is not the case, but in the context of other axioms, they are equivalent;[24] specifically, the well-ordering principle implies the induction axiom in the context of the first two above listed axioms and
Mathematical induction is a concept that helps to prove mathematical results and theorems for all natural numbers. The principle of mathematical induction is a specific technique that is used to prove certain statements in algebra which are formulated in terms of n, where n is a natural number. Any mathematical statement, expression is proved based on the premise that it is true for n = 1, n = k, and then it is proved for n = k + 1.
Mathematical Induction is a technique used to prove that a mathematical statements P(n) holds for all natural numbers n = 1, 2, 3, 4, ... It is often referred as the principle of mathematical induction. To prove a result P(n) using the principle of mathematical induction, we prove that P(1) holds. If P(1) is true, then we assume that P(k) holds for some natural number k, and using this hypothesis, we prove that P(k+ 1) is true. If P(k+1) holds true, then the statement P(n) becomes true for all natural numbers.
After proving these 3 steps, we can say that "By the principle of mathematical induction, P(n) is true for all n in N". The assumption that we make in the second step that P(n) holds for some natural number n = k is called induction hypothesis.
Example 1: Prove that the formula for the sum of n natural numbers holds true for all natural numbers, that is, 1 + 2 + 3 + 4 + 5 + .... + n = n(n+1)/2 using the principle of mathematical induction.
Mathematical induction is the process of proving any mathematical theorem, statement, or expression, with the help of a sequence of steps. It is based on a premise that if a mathematical statement is true for n = 1, n = k, n = k + 1 then it is true for all natural numbrs.
To prove a result P(n) using the principle of mathematical induction, we prove that P(1) holds. If P(1) is true, then we assume that P(k) holds for some natural number k, and using this hypothesis, we prove that P(k+ 1) is true. If P(k+1) holds true, then the statement P(n) becomes true for all natural numbers.
The different types of mathematical induction are:
First principle of mathematical induction
Second principle of mathematical induction
Second principle of mathematical induction (variation)
which is variously known as "strong" or "extended" induction, or the "second principle" of induction. While any such proof can be rewritten so as to use only "basic" induction (truth for $k$ implies truth for $k+1$), in the case of the FTA it is not very convenient to do so.
Induction can be useful in almost any branch of mathematics. Often, problems in number theory and combinatorics are especially susceptible to induction solutions, but that's not to say that there aren't any problems in other areas, such as Inequalities, that can be solved with induction.
Induction is also useful in any level of mathematics that has an emphasis on proof. Induction problems can be found anywhere from the Power Round of the ARML up through the USAMTS all the way up to the USAMO and IMO. A good example of an upper-level problem that can be solved with induction is USAMO 2006/5.
The problem is as follows: "Prove that (-2)0 + (-2)1 + (-2)2 + ... + (-2)n = (1 - 2n+1)/3 for every positive odd integer n." It's in a section of a textbook chapter that focuses on the first and second principles of mathematical induction, so I assume that one of those principles is required in order to solve the problem.
In case you can't read my handwriting: First, I (think) I proved P(1) by setting n equal to 1 on both sides of the equation, so that I had (-2)0 + (-2)1 = (1 - 21+1)/3, and simplifying it until I got -1 = -1, which is always true. Then I set up my inductive hypothesis P(k): (-2)0 + (-2)1 + (-2)2 + ... + (-2)k = (1 - 2k+1)/3. Finally, I attempted to prove P(k+1) by inserting k+1 in place of k and using algebra to manipulate the equation until I got (1 - 2k+2)/3 = (1 - 2k+2)/3, only that didn't work. I got to the step of (1 - 2k+2)/3 = (3(-2)k+1)/3 + (1 - 2k+1)/3 and realized that the right side isn't equal to the left side. So much for my attempt at using the first principle of mathematical induction. Then I tried using the second principle of mathematical induction, but I'm 99% sure I did that wrong, too. I don't really understand how to use the second principle of mathematical induction at all. A friend told me that I should plug in 3 as a value for r in this problem and solve from there, but I'm not even sure that you're supposed to plug in values for r... The last two lines on the bottom there are just me writing "The k+1 part is tripping me up because k must always be odd but an odd number + 1 is always even."
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