Understanding // in the Hint for Showing Numbers of Form ±m√2/n Are Dense

In summary, the "//" in the given hint stands for division and is used to find a rational number in a given interval. This is used to prove that the set of all irrational numbers of the form ±m√2/n is dense.
  • #1
strobeda
42
0
Hello,

Please, someone, explain what the // in the hint below stands for:

"Show that the numbers of the form
±m√2/n
for m, n ∈ N are dense."

Hint:
"To find a number in (x, y), find a rational in (x//√2, y//√2). Conclude from this that the set of
all (irrational) numbers of the form ±m√2/n is dense."

Thank you in advance.
 
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  • #2
strobeda said:
Hello,

Please, someone, explain what the // in the hint below stands for:

"Show that the numbers of the form
±m√2/n
for m, n ∈ N are dense."

Hint:
"To find a number in (x, y), find a rational in (x//√2, y//√2). Conclude from this that the set of
all (irrational) numbers of the form ±m√2/n is dense."

Thank you in advance.

I think it's a misprint for division, since if you take a rational in [itex](x/\sqrt{2},y/\sqrt{2})[/itex] and multiply it by [itex]\sqrt{2}[/itex] you indeed get a real number in [itex](x,y)[/itex].
 
  • #3
I suspected that, but I didn't want to go astray trying a wrong tack in case I was just ignorant of the symbol.

Thank you very much, pasmith.
 

1. What does the notation // represent?

The notation // represents the floor function, also known as the greatest integer function. This function returns the largest integer less than or equal to a given real number.

2. What does the term "dense" refer to in this context?

In mathematics, the term "dense" means that there are infinitely many elements in a given set or interval. In this context, it means that there are infinitely many numbers of the form ±m√2/n between any two given numbers.

3. How do I show that numbers of the form ±m√2/n are dense?

To show that numbers of the form ±m√2/n are dense, you can use the following approach:
1. Choose two arbitrary real numbers, x and y, such that x < y.
2. Express x and y in the form ±m√2/n.
3. Use the floor function to find the largest integer less than or equal to x and y.
4. Let k be the largest integer between x and y.
5. Express k in the form ±m√2/n.
6. Since k is the largest integer between x and y, there must be infinitely many numbers of the form ±m√2/n between x and y.

4. Can you provide an example to illustrate the density of numbers of the form ±m√2/n?

One example of the density of numbers of the form ±m√2/n is between the numbers 1 and 2. Let's choose n = 1 and m = 1. Then, the numbers of the form ±m√2/n between 1 and 2 are:
-1.41421356, -1, -0.41421356, 0, 0.41421356, 1, 1.41421356.
As you can see, there are infinitely many numbers of this form between 1 and 2.

5. How is this concept relevant in the field of mathematics?

The concept of density is relevant in many areas of mathematics, including number theory, algebra, and analysis. It helps us understand the distribution of numbers and the properties of different sets of numbers. In this particular context, the density of numbers of the form ±m√2/n is important in understanding the nature of irrational numbers and their relationship with rational numbers.

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