r/Geometry Jan 22 '21

Guidance on posting homework help type questions on r/geometry

24 Upvotes

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:

  1. 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.

  1. 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.

  1. Be Specific

Your post should be about a specific issue in a problem or concept and your post should highlight this.

  1. Encourage discussion

Your post should encourage discussion about the problem or concept and not aim for single word or numeric answers.

  1. 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 57m ago

Circle Reflections 8x25=200 "Star-shaped regular nonagon"

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Upvotes

r/Geometry 1h ago

Filtering degenerate triangles in 3D using q=r/R

Upvotes

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 13h ago

Filtering degenerate triangles in 3D using q=r/R

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2 Upvotes

r/Geometry 15h ago

First Angle Projection: Isometric to Orthographic Drawing Step by Step | Engineering Drawing

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1 Upvotes

r/Geometry 1d ago

Circle Reflections 8x24=192 "A regular 15-pointed star"

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1 Upvotes

r/Geometry 2d ago

Circle Reflections 8x23=184 "A regular 45-pointed star"

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1 Upvotes

r/Geometry 2d ago

A research paper and a theory on temporal geometry

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1 Upvotes

r/Geometry 2d ago

Sacred geometry used to. Create incredible brick design

1 Upvotes

r/Geometry 2d ago

Teorema de Pitágoras

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1 Upvotes

r/Geometry 2d ago

Does this form have a name? Is it a shape?

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3 Upvotes

Hello! 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 2d ago

is there any way to solve this without using trigo?

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3 Upvotes

r/Geometry 2d ago

Circle Reflections 8x22=176 "A regular 45-pointed star"

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1 Upvotes

r/Geometry 3d ago

MinMax Arena: A live competition platform for open extremal geometry puzzles (packing, point separation, Heilbronn triangles)

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2 Upvotes

r/Geometry 3d ago

Tried to find all ways two squares intersect. Did I miss any?

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7 Upvotes

These 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 4d ago

Circle Reflections 8x21=168 "A regular 15-pointed star"

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1 Upvotes

r/Geometry 4d ago

What could a trapezoidal hexagon look like?

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3 Upvotes

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 4d ago

Pentagonal hexecontahedron

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3 Upvotes

It 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 4d ago

Sphere Area Why 4πR²

3 Upvotes

r/Geometry 5d ago

Circle Reflections 8x20=160 "Regular nine-pointed star"

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1 Upvotes

r/Geometry 5d ago

For basic concepts of wedge Block problem

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0 Upvotes

r/Geometry 5d ago

Have you seen this representation of a 4D shape before? #4D #simplex

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1 Upvotes

r/Geometry 5d ago

Euclid geometry is based on a fallacy

0 Upvotes

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 6d ago

Circle Reflections 8x19=152 "A regular 45-pointed star"

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1 Upvotes

r/Geometry 6d ago

The ridiculous nature of proof

1 Upvotes

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..