Hyper-intriguing Ornament VI - A gentle ending

Probability Level pending

Once again, consider a hyper-ball i = 1 n x i 2 25 \sum_{i=1}^{n}{x_i}^2 \leq 25 and a concentric hyper-cube [ 4 , 4 ] n \left[-4,4 \right]^n in R 4 \mathbb{R}^4 . Given our answers to Part I and V , can we calculate the probability of finding the hyper-bug only in the hyper-spherical part of the ornament, given that it is stuck in the ornament? Provide your answer in percentage, rounded to the nearest integer. Write 101 101 if there is not enough information to find this probability.


The answer is 8.

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2 solutions

Otto Bretscher
Dec 31, 2018

Since this one is very similar to Part V, I will submit a very similar solution, Comrade ;)

At this point, it is all just a matter of "crunching the numbers". Let's summarize what we found in problem I, at the beginning of the saga. If B B is the volume of the ball and C C is the volume of the cube, then C = 8 4 = 4096 , B 3084 , B C = 8 V c a p s 379 , B C 2705 , C B = 1391 , B C = 4475 C=8^4=4096,\ B\approx 3084,\ B\text\ C=8V_{caps}\approx 379,\ B\cap C\approx2705,\ C\text\ B=1391,\ B \cup C= 4475 The probability we seek is B C B C 8 % \frac{B\text\ C}{B \cup C}\approx \boxed{8}\text\%

The Hyper-intriguing Ornaments have been fun (for a crowd of three,essentially), but every good thing must come to an end. Thank you, Comrade!

Thank you, Otto. Indeed, just like 2018.

Huan Bui - 2 years, 5 months ago

cap 4 ( r , h ) = 1 12 π ( 4 h 7 ( h 2 r ) 2 r ( r h ( h 2 r ) ( h + 3 r ) 6 h 5 ( h 2 r ) ) + 6 r 4 tan 1 ( h r h ( h 2 r ) ) + 3 π r 4 ) \text{cap}_4(r,h)=\frac{1}{12} \pi \left(-4 \sqrt{-h^7 (h-2 r)}-2 r \left(r \sqrt{-h (h-2 r)} (h+3 r)-6 \sqrt{-h^5 (h-2 r)}\right)+6 r^4 \tan ^{-1}\left(\frac{h-r}{\sqrt{-h (h-2 r)}}\right)+3 \pi r^4\right)

Because this is 4 dimensional, there are 8 caps, 8 cap 4 ( 5 , 1 ) = 2 3 π ( 1875 π 2232 3750 tan 1 ( 4 3 ) ) 379.356021363 8\ \text{cap}_4(5,1) = \frac{2}{3} \pi \left(1875 \pi -2232-3750 \tan ^{-1}\left(\frac{4}{3}\right)\right) \approx 379.356021363 .

2 π ( 1875 π 2232 3750 tan 1 ( 4 3 ) ) 3 ( 4096 + 2 3 π ( 1875 π 2232 3750 tan 1 ( 4 3 ) ) ) 0.0847656 \frac{2 \pi \left(1875 \pi -2232-3750 \tan ^{-1}\left(\frac{4}{3}\right)\right)}{3 \left(4096+\frac{2}{3} \pi \left(1875 \pi -2232-3750 \tan ^{-1}\left(\frac{4}{3}\right)\right)\right)} \approx 0.0847656

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