About the Product of Two Commuting Elements

In summary, an example of two commuting elements whose product does not have an order equal to the least common multiple of their individual orders is -1 and 1 in the set of integers. Their product, 0, has an order of 1, but the individual elements have an order of infinity. This is because the least common multiple of infinity and infinity is undefined. Instead, it is suggested to consider the set of remainders from division by 12, represented by the clock hand analogy.
  • #1
Bashyboy
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Homework Statement


I am asked to offer an example of two commuting elements whose product does not have an order equal to the least common multiple of their individual orders.

Homework Equations

The Attempt at a Solution


Consider ##-1## and ##1## in ##\mathbb{Z}##. Then ##1+(-1) = 0## which has an order of ##1##, but the order of ##-1## and ##1## is infinity.

Would this be an acceptable answer? I find it unsettling for some reason, but I cannot see anything wrong with it.
 
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  • #2
This looks a bit like cheating. What is the least common multiple of ##\infty## and ##\infty##?
You should consider ##( \mathbb{Z_{12}}\, , \,+) = (\mathbb{Z}/12 \mathbb{Z} \, , \, +)## instead, i.e. the remainders from division by ##12## or simply the little hand on the clock.
 

1. What is meant by "commuting elements" in the context of products?

"Commuting elements" refers to two elements in a mathematical system that can be rearranged in any order without changing the result of their product.

2. How does the product of two commuting elements differ from the product of non-commuting elements?

The product of two commuting elements is commutative, meaning the order in which the elements are multiplied does not affect the result. However, the product of non-commuting elements is not commutative and the order of multiplication does affect the result.

3. What are some examples of commuting elements?

In the context of matrices, diagonal elements are an example of commuting elements. In the context of real numbers, any two numbers are commuting elements.

4. Why is the property of commuting elements important in mathematics?

The property of commuting elements allows for simplification and ease of calculation in mathematical operations. It also helps in finding patterns and making predictions in mathematical systems.

5. Can more than two elements commute with each other?

Yes, in a mathematical system, it is possible for more than two elements to commute with each other. For example, in a group of four numbers, all four numbers can commute with each other.

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