Rationality test!

Algebra Level 2

Does there exist a case where:

Irrational Number Irrational Number = Rational Number {\text{Irrational Number}}^{{\text{Irrational Number}}}={\text{Rational Number}} ?

No Yes

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2 solutions

Tin Le
Jun 16, 2020

Take this example: 2 2 \sqrt{2}^{\sqrt{2}} .

If 2 2 \sqrt{2}^{\sqrt{2}} is a rational number, then the problem is solved.

If 2 2 \sqrt{2}^{\sqrt{2}} is an irrational number, then consider this case:

  • ( 2 2 ) 2 = 2 2 × 2 = 2 2 = 2 (\sqrt{2}^{\sqrt{2}})^{\sqrt{2}} = \sqrt{2}^{\sqrt{2} \times \sqrt{2}} = \sqrt{2}^2 = 2 (2 is, obviously, a rational number)

Therefore, there is always a case where an irrational number raised to the power of another irrational number results in a rational number.

Beautiful solution

After studying a little bit of log, I thought this would be a good problem.

a log a b = b a^{\log_{a}{b}} =b , putting any irrational number as a a and any rational number as b a 2 b \neq a^2 , we have infinite answers!

P.S. I need practice for log, as I just studied it today, so I may be wrong. Please comment if that is the case.

The word "any" is incorrect. For example, take a = b a=\sqrt b , where b b is square free. Then log a b \log_a b is rational. Otherwise your logic is correct.

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Oh, sorry Sir! I just studied log for the first time today, can you please tell me where I should correct it?

Vinayak Srivastava - 12 months ago

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Write "any b a 2 b\neq a^2 ".

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@A Former Brilliant Member Thanks, edited!

Vinayak Srivastava - 12 months ago

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