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Sep
25
revised How do I estimate log10 of log10 of 8 billionth element of A000670?
corrected estimate
Sep
25
revised How do I estimate log10 of log10 of 8 billionth element of A000670?
possible estimate
Sep
14
awarded  Tumbleweed
Sep
7
awarded  Popular Question
Sep
7
revised Map Earth surface so straight line distance is great circle distance?
triangle inequality
Sep
7
accepted Map Earth surface so straight line distance is great circle distance?
Sep
7
comment Map Earth surface so straight line distance is great circle distance?
OK, I see it now. Because the distance from the North Pole to the equator must be EXACTLY 1/2 the distance from the North Pole to the South Pole, the entire equator must map to one point, which obviously doesn't work. This also shows you can't do it within a specified tolerance.
Sep
7
revised Map Earth surface so straight line distance is great circle distance?
sines and cosines as part of mapping
Sep
7
comment Map Earth surface so straight line distance is great circle distance?
More symbols, please. Or, better still, could you pick 3-4 specific points and show why this would be impossible? I think the proof you give works even for the straight line distance between two points on Earth, and it's obviously possible to map those in R^3
Sep
7
comment Map Earth surface so straight line distance is great circle distance?
OK, but doesn't the equator just have to map to a set of points equidistant from the poles? It doesn't have to map to the midpoint of the poles?
Sep
7
comment Map Earth surface so straight line distance is great circle distance?
First answer: but what about the Earth in 3-D. Every point on the equator is equidistant from the poles, no? In 2D this would be the perpendicular bisector. In 3D, it's a plane. In n dimensions, it's an n-1 dimensional surface, no? Second answer: what if I wanted to specify the tolerance. Is there always an 'n' that satisfies for a given tolerance?
Sep
7
asked Simple formulas rotating Earth around xyz axes?
Sep
7
asked Map Earth surface so straight line distance is great circle distance?
Sep
6
answered Why do you add +1 in counting test questions?
Aug
31
comment Inquiries around a new number system
Also octonions which have 7 imaginary units, but aren't associative.
Aug
31
comment What shape does a piece of paper make when it is pushed from the edges?
This looks like an inverse catenary to me, but I could be wrong.
Aug
26
comment How do I estimate log10 of log10 of 8 billionth element of A000670?
I'd like to get it to the nearest integer at least. When you say "use Stirling on your upper bound", could you be more explicit? I assume you're referring to a Stirling approximation, but wasn't sure. Also, are the "&E9" supposed to be "8E9" referring to 8 billion? Sorry, no offense intended, just a little hard to read your post.
Aug
26
comment How do I estimate log10 of log10 of 8 billionth element of A000670?
@RossMillikan You are correct, it's (2^n)*n!, but wouldn't that be implied by order of operations anyway?
Aug
26
asked How do I estimate log10 of log10 of 8 billionth element of A000670?
Aug
4
comment Comparing the “sizes” of square roots.
Estimating Sqrt[5] as 9/4 works (once you confirm the approximation is within 1/8 of the true value).