Thursday, 24 July 2014

algebra precalculus - How to solve 2 tetrated 0.5 times?

I've been really interested in tetration lately. So I came up with a seemingly simple problem to solve, which is 2 tetrated 0.5 times, which I'll write as the following.



2^^0.5




To make sense of this notation, consider the following where A represents a real number:



A^A = A^^2



A^A^A = A^^3



etc.



Here's where my problem is. The answer I got and the one on Wikipedia are different. I'm assuming the answer on Wikipedia is the correct one, but I would like to know what I did wrong.




So here's how I tried to solve this problem:



First I say 2^^0.5 is the same as the "super square root" of 2 (I don't exactly know how to format this), which is equal to X.



Next I tetrate or "super square" both sides by 2, so the "super square root" of 2 becomes 2, and X becomes X tetrated 2 times, which looks like the following:



X^^2 = 2



Then I rewrite X tetrated 2 times as X to the power of X.




X^X = 2



Finally I graphed Y = X^X and Y = 2 on my calculator and found the intersection point in the first quadrant, which should be the answer of 2^^0.5. And I got the following:



X = 1.559610469 (approximately)



However, the answer to 2^^0.5 on Wikpedia is approximately 1.45933.



Does anyone know what I did wrong when trying to solve this problem? Any answers would be appreciated. Also, if you have any questions of what I did or what I'm asking, feel free to ask.

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