Irrational numbers vs. Transcendental numbers

In summary, the conversation discusses the definitions of irrational and transcendental numbers. It is stated that irrational numbers cannot be expressed as fractions, while transcendental numbers cannot be solutions to polynomial equations with rational coefficients. The lack of any repeating pattern is a key characteristic of irrational numbers, while transcendental numbers cannot be constructed using polynomial functions with 100% accuracy. The conversation also touches on the relationship between continued fractions for irrational and transcendental numbers.
  • #1
Wooh
47
0
It would seem that an irrational number would have to be a transcendental number. If a transcendental number is a number which goes on infinitely and never repeats, then all irrational numbers would have to be transcendental, because if they repeated then you could find a fraction doing the whole x = .abcdef... 1000000x=abcdef.abcdef... and so forth.
Are there any counter-examples?
 
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  • #2
First off:
Irrational means 'cannot be expressed as a fraction'. For example [tex]\sqrt{2}[/tex] is an irrational number.

Transcendental means is not a solution to any equation that contains only rational numbers. For example, [tex]\pi[/tex] is a transcendental number. [tex]\sqrt{2}[/tex] is not a transcendental number.
 
  • #3
Originally posted by NateTG
First off:
Irrational means 'cannot be expressed as a fraction'. For example [tex]\sqrt{2}[/tex] is an irrational number.

Transcendental means is not a solution to any equation that contains only rational numbers. For example, [tex]\pi[/tex] is a transcendental number. [tex]\sqrt{2}[/tex] is not a transcendental number.
Ah. Then I believe my problem was in my defintions, however, I was under the impression that transcendental meant it never repeated or whatnot. I guess this is more of a symptom. so, is root 2 not transcendental because it solves x^2 = 2? Wouldn't that make pi merely irrational, as it solves various series that converge at it, like x = 1 + 1/3 - 1/5 or however it goes.
Thanks for your time!
 
  • #4
Sorry, let me me more clear.
Transcendental numbers can never be expressed as the roots of polynomial equations. (Equations involving addition, multiplication, subtraction or division. No infinite series, logarithms, or trig functions.)
 
  • #5
Originally posted by NateTG
Sorry, let me me more clear.
Transcendental numbers can never be expressed as the roots of polynomial equations. (Equations involving addition, multiplication, subtraction or division. No infinite series, logarithms, or trig functions.)
Ah! That clears that up.
So is the lack of any repeating trademark to irrational numbers as a whole?
 
  • #6
Well, "lack of any repeating" isn't a good description, but that's essentially it, yes.
 
  • #7
Isn't that also (indirectly) stating that trancendental numbers appear in their own definition?
 
  • #8
Originally posted by On Radioactive Waves
Isn't that also (indirectly) stating that trancendental numbers appear in their own definition?

I don't understand what you mean.
 
  • #9
Originally posted by NateTG
Sorry, let me me more clear.
Transcendental numbers can never be expressed as the roots of polynomial equations. (Equations involving addition, multiplication, subtraction or division. No infinite series, logarithms, or trig functions.)

It's important to add that these polynomials have integer, or rational, or algebraic coefficients. In other words you can't get transcendental numbers from polynomials with coefficients that aren't transcendental.
 
  • #10
What is the relationship between continued fractions for irrational numbers and how exactly does this differ from the continued fractions of transcendental numbers?

Also wondering: transcendental functions (trig and log functions, infinite series): completely impossible to construct out of polynomial functions with 100% accuracy?
 
  • #11
selfAdjoint said:
It's important to add that these polynomials have integer, or rational, or algebraic coefficients. In other words you can't get transcendental numbers from polynomials with coefficients that aren't transcendental.

Yes, otherwise x = pi would satisfy criteria. Also in same spirit x = sqrt(2) square both sides and you recover 2. x = pi what do you do now? what do you recover using allowed operations on polynomials? what is inside pi and how do you get it out? LOL

1/sqrt(2) rationalize the denominator...very easy.

1/pi rationalize the denominator...you become FAMOUS!
 

What is the difference between irrational numbers and transcendental numbers?

Irrational numbers are numbers that cannot be expressed as a ratio of two integers, while transcendental numbers are numbers that cannot be expressed as the root of a polynomial equation with integer coefficients. In other words, all transcendental numbers are irrational, but not all irrational numbers are transcendental.

How do you prove that a number is irrational or transcendental?

The most common method to prove a number is irrational is by contradiction, assuming the number can be expressed as a ratio of two integers and showing that it leads to a contradiction. To prove a number is transcendental, one must show that it is not a root of any polynomial equation with integer coefficients.

What are some examples of irrational and transcendental numbers?

Some examples of irrational numbers include pi (π), the square root of 2 (√2), and the golden ratio (φ). Examples of transcendental numbers include e, which is the base of the natural logarithm, and the Euler-Mascheroni constant (γ).

Why are irrational and transcendental numbers important in mathematics?

Irrational and transcendental numbers play a crucial role in mathematics as they provide a counterexample to the common belief that all numbers can be expressed as a ratio of two integers. They also have many applications in various fields, such as physics, engineering, and cryptography.

Can irrational and transcendental numbers be approximated?

Yes, irrational and transcendental numbers can be approximated using decimal expansions or continued fractions. However, these approximations are not exact and will always have a margin of error. This is because irrational and transcendental numbers have infinitely many digits after the decimal point and cannot be expressed as a finite decimal or fraction.

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