/r/Geometry
/r/Geometry
8,070 Subscribers
How would you measure degrees rotation of a human head/face between 2 photos?
I have 1 photo of me looking direct at my camera second photo i've turned my head looking slightly to the right. How would I work out degrees turned on a 3D image like this. Thanks.
10:55 UTC
Distance Between Arbitrary Points on Inner and Outer Circles of Annulus
Hi,
I was wondering, given the following diagram which I've put together:
It comprises of:
- An annulus has a center at point O with two circles of radius r1 and r2.
- 2 fixed points, Z and W.
- Z is regarded as 0° reference and bisects both circles at point O
- W is regarded as 90° and is at right angles to Z and also bisects both circles at point O
- 5 arbitrary points, denoted by A, B, C, D, and x.
- The angle of Z→O→x is known.
- The angle of Z→O→A is known, and the same applies to B, C, and D.
Feel free to assign any value you wish to r1 and r2 provided that r1 is smaller than r2 when trying to explain if you could :-) And use any angles for ZOx, ZOA, .... etc... I didn't want to give any values as it'd probably be easier for whoever looks at this.
My question is:
What is the proper way to work out:
The length of:
- x → A
- x → B
- x → C
- x → D
The angle between the :
- Tangent at x → A and the orientation of Z
- Tangent at x → B and the orientation of Z
- Tangent at x → C and the orientation of Z
- Tangent at x → D and the orientation of Z
I'm just working on a personal astronomy hobby thing and not quite sure how to work the above out... Geometry was over 35 years ago for me so I'm a little rusty, but I'm sure that there's a guru here who can help :-)
Look forward to help with this!
Thanks for being patient, I had to retype all of this haha.
Cheerio..
Cabbage
20:35 UTC
Opposing Lines
If I do an image search for "opposing lines," I get images of lines that cross each other. I would expect them to be parallel to each other like an opposite wall. Shouldn't they have to be?
17:26 UTC
is this true?
i'm making a non-euclidean game and want to verify this
is it true?
01:06 UTC
What are good resources for visually interactive geometry calculations?
I was reading Feyman’s “Six Not So Easy Pieces” and embarrassed by how slowly I was getting the translation between coordinate systems—what exactly was x vs y times sin vs cos. I understand the principles behind them, but I want to be able to break it down in my head much faster, and i am sure there are some nifty tools floating around out there for such basic and less basic things. Do you have any recommendations?
19:38 UTC
prove ED = DH
doing some self learning by watching PreMath videos on youtube. I came across this question. the question is easy to answer, but it makes a assumption that ED = DH. by looking at the diagram, it seems a fair assumption, but i cannot seem to prove this rigorously. would it be possible to rotate the rectangle such that AC is not parallel to EH, thereby making ED not equal to DH? can someone help please.
Notes:
ABCD is a square with a diagonal length of 9√2
EFGH is an inscribed rectangle with long side length of 8
Find area of EFGH
14:18 UTC
hmmm
since you can't fit a euclidean space into any spherical space, but any spherical space into a euclidean space, what if there's a space that contains euclidean geometry?
04:21 UTC
i am so happy right now
i am thinking of making a non Euclidean game and
IS IT TRUE???
04:20 UTC
Again.
I don't do the messages on here because even when they work it's tough to use from a phone. Please email if you have legitimate questions or comments. Jameson.b.garnett@gmail.com I'm delusionally confident because I am right. So either save your self the argument, or just be a nice human being. Nearly everyone I talk to on here has no idea how stupid they are and they believe that pointing out how simple something is - makes them superior. I know how simple this all is. See I know things like when you want the exact conversion for a 5 radius from line to /arc... you simply need to multiply pi by the square root of 50, and divide by 4. Because that's just using the circumference of another circle and dividing out one of its quarters, which is all pi does - it is a percentage conversion. It is 4 sets of .785398etc. The number we use. Is all of the 4ths combined and very much should be seen as such. That... is how you stop "approximating" pi. You use it correctly.
Again... none of you will likely comprehend that and if you do - you will recall some textbook version and you will miss the literal, infinite number of incredible things that one simple fact opens up for you, and potentially the rest of the world. It's truly tragic. If you're alive and awake and see this please email me, this not about people like you 👌
04:07 UTC
What is the name of this polyhedron?
I have searched all over the place and can't find anything. The only thing with a remotely similar appearance to me is the snub cube, but this is distinctly different.
Heeeelp I'm going insane!!!
11:43 UTC
pixelated pi
A thought popped in my head just now about pixelated circles, specifically the number of pixels in the circumference as a ratio compared to the diameter, or a pixelated value of pi.
Because some pixels are traversed diagonally and these have a length of 1.41 pixels, as the diameter increases it should approach a value for pi that is lower than actual pi.
My intuition says ~2.828, or 2*sqrt(2) or 4*sin(45) but I haven't put pen to paper yet.
That's all, just thought someone else in here might find it interesting to think about.
07:35 UTC
What is the name of this shape/polygon?
Is this a stallated tetradecagon of something else?
07:12 UTC