Irrational Number Checker
Check whether a number is rational or irrational. Test integers, decimals, square roots, and famous constants like pi and e. Includes mathematical proofs and explanations.
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Result
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Formula
Rational numbers can be written as a fraction of two integers (e.g. 0.75 = 3/4). Irrational numbers have non-terminating, non-repeating decimals and cannot be expressed as any fraction. Examples: pi, e, sqrt(2), and the golden ratio.
Worked Example
What Is an Irrational Number?
- Irrational numbers cannot be written as a fraction of two integers.
- Their decimal expansions are non-terminating and non-repeating.
- Famous examples include pi (π), Euler's number (e), and the square root of 2 (√2).
- They are essential in advanced mathematics, geometry, and engineering.
Distinguishing between rational and irrational numbers is key to many mathematical problems. Use our Irrational Number Checker to effortlessly classify numbers and deepen your understanding of these fascinating mathematical entities.
You can also calculate changes using our Fraction Calculator or Percentage Calculator.
Frequently Asked Questions
Is pi an irrational number?
Yes. Pi (3.14159265...) is irrational. Johann Lambert proved this in 1761. Pi is also transcendental, meaning it is not a root of any polynomial equation with integer coefficients.
Is sqrt(2) irrational?
Yes. The square root of 2 (approximately 1.41421356...) is irrational. This was proven by the ancient Greeks using proof by contradiction, and is one of the most famous results in mathematics.
How can I tell if a square root is irrational?
The square root of a positive integer is rational only if that integer is a perfect square (1, 4, 9, 16, 25, 36, ...). All other positive integer square roots are irrational.
Are all decimals irrational?
No. Terminating decimals (like 0.75) and repeating decimals (like 0.333...) are rational. Only non-terminating, non-repeating decimals are irrational.
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