Haiku: My Favorite Number

Algebra Level 3

I really like x . \text{I really like }x. x is one n th and half n . x\text{ is one }n\text{th and half }n. Find positive x . \text{Find positive }x.


This is my second entry to the (unofficial) Math Poetry Contest .


The answer is 0.7071.

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3 solutions

Levi Walker
Oct 31, 2018

One nth, but a third won’t do \text{One nth, but a third won't do} x is half n, that much is true \text{x is half n, that much is true} So n squared must be two! \text{So n squared must be two!} And x, I won’t forget you \text{And x, I won't forget you} Because you are half n, 2 / 2 ! \text{Because you are half n, } \sqrt{2}/2!

Ha! I really liked this; it made me smile! Although the meter is a bit off, this is still very creative.

Blan Morrison - 2 years, 7 months ago

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Thanks! A poetic problem deserves a poetic solution :)

Levi Walker - 2 years, 7 months ago
Blan Morrison
Oct 30, 2018

First and foremost, one n n th is simply 1 n \frac{1}{n} , like how one tenth is 1 10 \frac{1}{10} , one eleventh is 1 11 \frac{1}{11} , etc.

1 n = x = n 2 \frac{1}{n}=x=\frac{n}{2} 1 n = n 2 \implies \frac{1}{n}=\frac{n}{2} 2 = n 2 2=n^2 n = ± 2 n=\pm \sqrt{2}

This means that x = 1 2 = 2 2 . 7071 |x|=\frac{1}{\sqrt{2}}=\frac{\sqrt{2}}{2}\approx .7071 β \beta_{\lceil \mid \rceil}


Personal note : This is my favorite number for multiple reasons. Firstly, it is simultaneously half of a number and the inverse of that same number (as seen in the middle of the last equation; it's a simple yet cool identity). Secondly, it appears in trigonometry and complex algebra very frequently ( i ± ( . 7071 + . 7071 i ) \sqrt{i}\approx \pm(.7071+.7071i) ; sin ( π 4 ) = cos ( π 4 ) . 7071 \sin (\frac{\pi}{4})=\cos (\frac{\pi}{4})\approx .7071 ). Lastly, it is very dear to me because it is a testament to how, not just in mathematics, there is no singular correct way to express and idea or solve a problem.

Fair enough. I was puzzled by the wording...had me thinking x = 1/n + n/2.

Orrin Ahola - 2 years, 7 months ago

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Yeah, I was kinda worried; it's hard to work with only 7 syllables! I figured most people could deduce that that wouldn't have an answer, and they would realize what I actually meant.

Blan Morrison - 2 years, 7 months ago

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Yeah, that's what should have happened. I realized this in retrospect. Good haiku.

Orrin Ahola - 2 years, 7 months ago
Aparna Phadke
Feb 23, 2019

1/n = n/2 n = square root of two. Therefore X = 0.7071

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