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I'm not sure what you mean, could you elaborate?

The post says that for a torus, which is a product space of two (or more?) circles, we can analyze the the distance "along each circle" from a shared origin for a chosen basis. One circle is our "x" and the other is our "y". (Contrast with a plane and two lines.)

This seems reasonable if the objects we're looking to measure our distance to are expressed in terms of those circles as well, since this allows us to simply put a measure on each circle and get a distance formula for any two points that behaves the way we would like.



I'm out of my depth but I believe it's a torus because it's 2 cylinders, not circles?


A cylinder is a circle and a line. The circle goes around and the line is the height.

A torus is a circle and a circle. One circle goes from the outside to the inside and back around, and the other goes around the outside, if we're talking about a donut. We can see that any point on the surface of the donut is some combination of "go around the outside" and "walk around towards the center". You can also imagine taking a cylinder and bending it around to make a torus -- this changes the 'height' line into a second circle.

We're talking about the product space, so what that means is you can describe the space by (two) coordinates, one drawn from each "shape" (actually, manifold). A "torus" then differs from a "plane" in that you can wrap around in the x-direction and wrap around in the y-direction, independently, since the x-direction on a torus is a circle instead of a line and the y-direction on a torus is a circle instead of a line. By contrast, a cylinder you can only wrap around one way, because you can only wrap in the direction that has a circle for its coordinate space.


You cannot take a piece of paper (of any size) and wrap it around part of a donut.


I'm not sure what you're trying to say, could you elaborate?




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