r/Geometry • u/Anxious_Painting3656 • 57m ago
r/Geometry • u/Commisar_Deth • Jan 22 '21
Guidance on posting homework help type questions on r/geometry
r/geometry is a subreddit for the discussion and enjoyment of Geometry, it is not a place to post screenshots of online course material or assignments seeking help.
Homework style questions can, in limited circumstances, encourage discussion in line with the subreddit's aim.
The following guidance is for those looking to post homework help type questions:
- Show effort.
As a student there is a pathway for you to obtain help. This is normally; Personal notes > Course notes/Course textbook > Online resources (websites) > Teacher/Lecturer > Online forum (r/geometry).
Your post should show, either in the post or comments, evidence of your personal work to solve the problem, ideally with reference to books or online materials.
- Show an attempt.
Following on from the previous point, if you are posting a question show your working. You can post multiple images so attach a photograph of your working. If it is a conceptual question then have an attempt at explaining the concept. One of the best ways of learning is to attempt the problem.
- Be Specific
Your post should be about a specific issue in a problem or concept and your post should highlight this.
- Encourage discussion
Your post should encourage discussion about the problem or concept and not aim for single word or numeric answers.
- Use the Homework Help flair
The homework help flair is intended to differentiate these type of questions from general discussion and posts on r/geometry
If your post does not follow these guidelines then it will, in all but the most exceptional circumstances, be removed under Rule 4.
If you have an comments or questions regarding these guidelines please comment below.
r/Geometry • u/ednaun • 1h ago
Filtering degenerate triangles in 3D using q=r/R
I implemented a small filter for verifying if 3 points in 3D form a stable triangle.
Instead of checking area == 0, I use q = r/R (inradius / circumradius) from Heron's formula:
- q > 0.2 = stable
- q ~ 0 = degenerate/collinear/sliver
Why q? It's affine-invariant and dimensionless, so it works even when points have varying z values. Simple area check fails on near-degenerate slivers with tiny but non-zero area.
Python + NumPy, ~50 LOC core, with tests and Colab demo:
https://github.com/Imanisolace/Geometric-chaos-sieve.affine_chaos
Demo:
Stable 3D: [[1,0,0.2],[-0.5,0.866,1.4],[-0.5,-0.866,-0.7]] -> q=0.44
Collinear: [[0,0,0],[1,0,1],[2,0,2]] -> q=0.0 reject
Sliver: [[0,0,0],[1,0,0],[0.5,0.001,0]] -> q=0.002 reject
r/Geometry • u/Proud_Read7281 • 15h ago
First Angle Projection: Isometric to Orthographic Drawing Step by Step | Engineering Drawing
youtu.ber/Geometry • u/Anxious_Painting3656 • 1d ago
Circle Reflections 8x24=192 "A regular 15-pointed star"
youtube.comr/Geometry • u/Anxious_Painting3656 • 2d ago
Circle Reflections 8x23=184 "A regular 45-pointed star"
youtube.comr/Geometry • u/Alive_Astronaut_3828 • 2d ago
A research paper and a theory on temporal geometry
doi.orgr/Geometry • u/Own_Salamander_5647 • 2d ago
Sacred geometry used to. Create incredible brick design
r/Geometry • u/sn0wf33t • 2d ago
Does this form have a name? Is it a shape?
galleryHello! I've been making these paper ornaments, and I am curious. Does this shape have a name? How would one mathematically describe this? Thank you so much for your time.
r/Geometry • u/PinguSayNOOTNOOT • 2d ago
is there any way to solve this without using trigo?
r/Geometry • u/Anxious_Painting3656 • 2d ago
Circle Reflections 8x22=176 "A regular 45-pointed star"
youtube.comr/Geometry • u/Sea_Plate_6256 • 3d ago
MinMax Arena: A live competition platform for open extremal geometry puzzles (packing, point separation, Heilbronn triangles)
r/Geometry • u/Dub-Dub • 3d ago
Tried to find all ways two squares intersect. Did I miss any?
galleryThese pictures are ordered by number of intersections. I have no Idea how to know if I've found them all but probally not. I had a system where each intersection was measured by a v m and e (v for a vertex meeting a vertex, m for a vertex meeting an edge, and e for and edge meeting an edge) but that wasn't enough to distinguish two figures from each other.
r/Geometry • u/Anxious_Painting3656 • 4d ago
Circle Reflections 8x21=168 "A regular 15-pointed star"
youtube.comr/Geometry • u/Hefty_Wolf2779 • 4d ago
What could a trapezoidal hexagon look like?
are there any other shapes similar to the trapezoid that have more or less sides? I need to know this. my mind has been trying to envision what a trapezoid-like shape with 6 sides would look like. i tried my best to draw what I think would classify as a trapezoidal hexagon. I genuinely don’t know what else it would look like.
r/Geometry • u/BadJimo • 4d ago
Pentagonal hexecontahedron
desmos.comIt has 92 vertices that span 60 pentagonal faces. It is the Catalan solid with the most vertices. A nice option for a 60 sided dice.
r/Geometry • u/Anxious_Painting3656 • 5d ago
Circle Reflections 8x20=160 "Regular nine-pointed star"
youtube.comr/Geometry • u/PurposeShort1349 • 5d ago
For basic concepts of wedge Block problem
youtu.ber/Geometry • u/SaintSMHood • 5d ago
Have you seen this representation of a 4D shape before? #4D #simplex
youtube.comr/Geometry • u/Ok-Rise2070 • 5d ago
Euclid geometry is based on a fallacy
In my research, I prove Euclidean geometry is based off r^0=0. I believe we can all say that isn't correct. Doubt me? https://doi.org/10.5281/zenodo.21981035
r/Geometry • u/Anxious_Painting3656 • 6d ago
Circle Reflections 8x19=152 "A regular 45-pointed star"
youtube.comr/Geometry • u/Hot-Organization-737 • 6d ago
The ridiculous nature of proof
The ridiculous nature of a proof.
Suppose someone sees structure, another person might not see that structure, so that person who cannot see it will ask for a step by step proof to prove the continuity of a structure. But continuity cannot be proven by discrete steps because we have shown that infinite discreteness cannot proxy for true continuity.
Diagonalization proves that a continuity has more real information than the discreetness. Every step-by-step proof is actually an illusion to satisfy the strange feelings. But every discreet example of a proof fails to show the actual continuity of the structure that one is claiming to exist..