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Nine Pointed Sphere (Posted on 2021-06-03) Difficulty: 3 of 5
Show how to distribute nine points around the surface of a sphere in such a way that each point is equidistant from its four nearest neighbors.

No Solution Yet Submitted by Danish Ahmed Khan    
Rating: 3.0000 (2 votes)

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re(2): Solution -- Using spherical trig | Comment 6 of 12 |
(In reply to re: Solution -- Using spherical trig by Charlie)

As your solution is different from mine, I thought I'd add a variable to see how yours looks.  

The way I mapped 3D coordinates (turning circles into ellipses with 1/4 the height, then applying a vertical shift) does cause some distortion (since it doesn't move the north and south poles).  
I was worried that my solution (x=3/5, h=3/5 on Desmos) looks a bit too low, but again its hard to know.

Your latitude corresponds to h=sqrt(5)/3
and I added a width variable w=2/3

It does look better.  https://www.desmos.com/calculator/a2s7jvcska
And now you can make h any value you wish.

I didn't look closely at your formula.  I've never learned spherical trig either.  I remember a perplexus problem years ago that required it.

  Posted by Jer on 2021-06-04 12:29:12
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