## Finding near-misses between lines in 3D

Is there a good (read: well-known/efficient) way to find the "near-miss" intersection of 3 lines in 3D space? The lines almost, but don't quite, cross each other (image in an attempt to illustrate the problem)
posted by btfreek on Oct 14, 2016 - 6 answers

## math/geometry/construction query!

Suppose you have to install new moulding in a house. Suppose also that it's a huge house with many rooms large and small, and many windows of different size. This means that you end up needing many different lengths of wood...
posted by Rich Smorgasbord on Oct 6, 2016 - 14 answers

## Fano Plane and Hexagonal Tiling - a deep connection or a shallow one?

I've been chewing on the Fano plane a lot these last few weeks, and have just noticed something that seems really interesting to me. Notably, that the seven lines of the plane map very nicely to the 7-color hexagonal tiling.
posted by NMcCoy on Aug 11, 2015 - 10 answers

## Is there a name for this shape?

What would you call the shape of the two-dimensional outline of the two stones (cabochons) circled in red in this picture?
posted by sparklemotion on May 27, 2015 - 7 answers

## Books/review of high school math for former math major, current tutor

I need book recommendations two categories: 1) for myself for review (that are somewhere between high school text books and Spark notes) 2) just straight up textbooks for high school math (algebra i, geometry, algebra ii, trigonometry, pre-calculus)
posted by miss so and so on Mar 5, 2015 - 10 answers

## I know enough calculus to think of the question but not the answer

You want to walk 10 blocks north and 10 blocks east. It would be shorter to walk along the hypotenuse, but the same distance to walk 1 block north, then 1 block east, then 1 block north, etc. it seems that if the blocks were infinitesimally short, it would approximate the hypotenuse, but alas, walking 10 blocks in one direction and then 10 blocks in the perpendicular direction is the same as dividing it up. What gives?
posted by i_am_a_fiesta on Feb 2, 2015 - 20 answers

## Vicarious Math Pressure

My eldest child is starting high school. She is in the most advanced math class (a version of geometry) offered by her fairly demanding high school. But my eldest is struggling during the review of algebra -- rate problems, word problems, etc. Concerned because math is cumulative, and I don't want her falling behind. What can I do to help, both with math and with preventing her from becoming discouraged?
posted by Slap Factory on Oct 10, 2014 - 9 answers

## Help with 2D transforms in ellipse drawing algorithm

I'm trying to draw a 3D ellipse with a 2.5D graphics engine (Core Animation layers) which allow me to only compose my ellipse with line segments that must be moved into place using rotations and translations. I'm having trouble with the order of operations and can't get it to draw properly. Any graphics gurus or game programmers out there who can help me?
posted by krunk on Sep 1, 2014 - 7 answers

## Pythagorean Theorem in the original Greek

I'm looking for a textual version of a2 + b2 = c2 that is as old as possible, among all the Greek sources.
posted by benito.strauss on May 12, 2014 - 5 answers

## Tools For the Spatially Challenged: Couch-Movers Edition

Wizards of Hive, Before I buy that 90" couch from a friend, how can I make sure I'll be able to get it up my L-shaped stairs? Sure, there are a lot of variables. But is there a tool or methodology for figuring this out ahead of time (presuming I know the depth and height of the couch too)? I don't think I have the cardboard to build a mockup. This couch is 50 miles away and can't be returned. Thanks!
posted by baseballpajamas on Aug 21, 2013 - 14 answers

## Longitude lines in perspective, what shape are they?

I'm drawing/painting a globe (in time lapse, so the sun appears to rise) and trying to figure out what shape, exactly, the longitude (not latitude) lines are when a globe is flattened into a circle (I know I can just trace them, but I've gotten curious). So, the outermost longitude lines are tangent to the circle, they are half-circles, and the centermost line is a straight line from pole to pole, it's the progressively flatter curves in between that I'm trying to figure out. Do they have a name? Are they catenaries? Are they the curves of progressively larger circles? How do I construct them (easily)? Example image: HERE
posted by sexyrobot on Jul 26, 2013 - 11 answers

## What is the point at this!

Here’s a simple computational geometry problem. I am trying to figure out the value at an point of two line segments based off of the values at both of one of the segment’s endpoints. The problem is that I don’t exactly know the best way of going about finding the value at one of those points. Here is a reference figure. Given values (X_C, YC) = F_C (X_D, YD) = F_D How can I calculate the value of F_E, where F_E = (X_E, Y_E), where E is the point on the segment CD, where CD intersects with the line AB? (Extraneous details inside)
posted by oceanjesse on Dec 5, 2012 - 10 answers

## Math is Hard (I need help)

posted by anastasiav on Jul 22, 2012 - 11 answers

## The Limits of Flatness

Are there an infinite number of 2D shapes?
posted by mwachs on Jul 19, 2012 - 17 answers

## Identifying urban centers using an algorithm based on topological prominence

Calling geographers: has anyone applied the idea of topological prominence to population density?
posted by miyabo on Apr 27, 2012 - 7 answers

## I need an awesome topic relating to maps/geometry!

I'm looking for an awesome video/discussion topic that relates to street maps - something appropriate for a HS geometry course.
posted by ch3cooh on Jan 3, 2012 - 7 answers

Several years ago, I saw a website with a fun little flash or javascript applet thingy where you could build little tensegrity structure creatures, then have oscillating movements applied to the pieces, so that the structures would seem to "walk". I don't remember what it was called! From memory, one of the simpler structures looked sort of like this. What was it? Is it still online?
posted by rivenwanderer on Jan 3, 2012 - 4 answers

## I still KNOW the quadratic equation, just not what it means

I have forgotten basically all of math, and I want to learn it again from the ground up.
posted by showbiz_liz on Oct 19, 2011 - 28 answers

## Seperating Interlocked Rings

Consider two rings that are intertwined. (These lie in 3-dimensional space, but when you draw it on paper it looks like a venn diagram.) In 3-dimensional space they cannot be unlinked. The questions is, if you had one more dimension, can you unlink them?
posted by gzimmer on Jul 15, 2011 - 14 answers

## For best fireworks viewing, please use Math.

I'd like to be able to watch the Macy's fireworks from my dad's roof on the Upper West Side. How can I figure out if I'll be able to see them? I have some variables, heights, distances, and video...
posted by thebazilist on Jul 1, 2011 - 7 answers

## Formula to mesh two gears of arbitrary tooth count/position?

I'm writing a graphics app where I'm generating a simple gear transmission system with a variable number of gears each with variable number of teeth and placed at random orbits around each other. I generate gears in succession, placing and rotating each with respect to its parent/driver gear before moving on to the next. The problem I'm having is how to determine the initial orientation of each subsequent gear such that its teeth are properly meshed with that of its driver.
posted by Epsilon-minus semi moron on Oct 25, 2010 - 6 answers

## An awesome vector geometry teaching website

I'm trying to find a website that teaches vector mathematics in lesson form.
posted by giggleknickers on May 3, 2010 - 2 answers

## Regular tessellations of Euclidean spaces

MathFilter: Is there a relationship between the number of dimensions in a Euclidean space and the number of regular tessellations of that space?
posted by jedicus on May 2, 2010 - 10 answers

## Get thee gone, my polygon

I've got a polygon of n points. How can I simplify out noisy edges?
posted by soma lkzx on Mar 31, 2009 - 12 answers

## spherical geometry!

can you help me compute the area of a triangle on the sphere?
posted by klanawa on Feb 4, 2009 - 20 answers

## creating circles from rectangles

Math filter: How many equally sized rectangles will fit into a circle, and how should I arrange them in order to make the best-looking approximation?
posted by brandnew on Aug 17, 2008 - 9 answers

## It's been 24 years. I give up.

My geometry teacher in high school in 1984 showed us this puzzle. I was only half paying attention, but I believe the goal was to draw a line that intersected each segment only once.
posted by mecran01 on Jan 6, 2008 - 15 answers

## Two spheres colliding

Help me with the math of two spheres colliding
posted by RobotHero on Jun 10, 2007 - 8 answers

## How can I work out if a point x,y,z is contained by a cone ?

How can I work out if a point x,y,z is contained by a cone ?
posted by matholio on Jan 14, 2007 - 15 answers

## rotation shmotation

Vector Geometry Filter: I'm working in matlab and need to transform a surface to match an arbitrary angle. I have the unit vector of the new normal (and the original normal is in the Z axis (0 0 1))...however i'm not sure how to rotate one normal to another (i know, i know, it sounds very simple really...)
posted by NGnerd on Oct 23, 2006 - 5 answers

## help with triangles

My room has an angled ceiling. I have measured its height at the highest and lowest points, and I have the dimensions of the room. Help me determine what height the ceiling is at a particular point on the floor, and where exactly the skylight is.
posted by xo on May 23, 2006 - 11 answers

## I'm spaced out!

Programming/geometry: in a Flash program (you don't need to know Flash to answer this), I'm trying to place rectangular images at random positions on the screen. There are already images on the screen. I need to make sure that the new, randomly-placed images don't obscure the images already there.
posted by grumblebee on Sep 29, 2005 - 25 answers

## Not the golden rectangle

Is there a specific name for a rectangle which, if you divide it in half, the two halves have the same proportions as the original rectangle?
posted by e-man on Sep 27, 2005 - 12 answers

## Remember the Spirograph?

Remember the Spirograph?
posted by lorbus on Jul 11, 2005 - 13 answers

## Practical puzzle for math geeks

I have a circular patio table with four legs. The paving stones are uneven, so it has always been difficult to set the table in place so it doesn't wobble. I move it regularly, since the shadows from the trees change, and sometimes I want shade, other times sun. I used to mark small dots on the stones so I could set it down quickly. Then I discovered something very interesting--no matter where I put the table, if I simply rotate it around its center, I can very quickly find a steady configuration. But move it from place to place, and it takes all day. This is like the four color map theorem. It works every time, but I haven't figured out why. It might even be tricky to put this into a mathematical format. The table doesn't need to be level, and all four legs needn't be the same height or "at" the same height. The table just can't wobble. Go geeks.