Is the Square Root of 2 an Irrational Number?

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In summary, the conversation discusses the proof that the square root of 2 is irrational. The proof involves showing a contradiction by expressing m and n as products of prime numbers. This same method can be applied to any prime number or natural number that is not a perfect square. An alternative proof using the rational zero theorem is also mentioned.
  • #1
ltkach
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SquareRoot 2 is Irrational?

[itex]\sqrt{}2[/itex] I've attached an image of what I'm talking about. Tell me what you think.
 

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  • #2
Yes, that is the standard proof.
 
  • #3
Aren't you basically saying that assuming that ##\sqrt{2}## can be written as a rational number, then it is a rational number?
 
  • #6
DrClaude said:
Thanks. The last part, namely showing the contradiction, was missing from the OP.

i didn't think that the proof was complete until you express m and n as products of prime numbers. because of the squaring, there will always be an even number of any prime factor in both m2 and n2. but with the extra 2 (or whatever the prime number) on one side, you can show that equality is not possible, thus the proof by contradiction.

it's the same for the square root of any prime number. it cannot be rational.
 
  • #7
I have no experience with upper level math. I am barely in ODE. Anyways, someone showed me this and I thought it was amazing. Basically everything I learned is wrong.
 
  • #8
what are it's implications in math?
 
  • #9
ltkach said:
Basically everything I learned is wrong.

Had you learned that ##\sqrt{2}## was rational?
 
  • #10
rbj said:
it's the same for the square root of any prime number. it cannot be rational.

It's the same for any natural number that is not a perfect square (actually, the n'th root of any natural number that is not a perfect n'th power is irrational).

FYI. An easier proof uses the rational zero theorem. Consider the possible rational roots of the polynomial ## x^2 - 2 = 0 ##.
 
  • #11
wow i cannot believe myself. yeah ignore me.
 

What is the definition of an irrational number?

An irrational number is a real number that cannot be expressed as a ratio of two integers. In other words, it cannot be written as a fraction in the form of a/b where a and b are integers.

Why is Square Root 2 considered an irrational number?

Square Root 2 is considered an irrational number because it cannot be expressed as a ratio of two integers. Its decimal expansion is non-terminating and non-repeating, meaning it goes on infinitely without following a specific pattern.

How was it proven that Square Root 2 is irrational?

The proof that Square Root 2 is irrational was first demonstrated by the ancient Greek mathematician Pythagoras. A more formal proof was later developed by the Greek mathematician Euclid in his book "Elements". It involves assuming that Square Root 2 can be expressed as a ratio of two integers, and then using logical deductions to show that this assumption leads to a contradiction.

Can any square root be irrational?

No, not all square roots are irrational. Some square roots, such as the square root of 4, can be expressed as a ratio of two integers (in this case, 2). These are called rational square roots.

What are some real-world applications of understanding irrational numbers?

Irrational numbers are used in various fields such as physics, engineering, and computer science. For example, the value of pi (π), which is an irrational number, is used in calculations involving circles and spheres. In computer science, irrational numbers are used in algorithms for tasks such as generating random numbers or calculating the speed of an object.

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