Coordinate charts to cover a circle?

In summary, the conversation discusses the number of charts needed to cover a circle and a sphere. It is agreed that two charts are the minimal number for a circle, with one covering the upper half and the other covering the lower half. For a sphere, six charts can be used but two is the minimal number, which is typically found using stereographic projection.
  • #1
pivoxa15
2,255
1
4 charts seem to cover it. BUt only 2 will do for a minimal number?

Just like 2 charts will do to cover a sphere? Even though there are 6 all together.
 
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  • #2
I'm not sure why you add that "6 altogether". What 6 charts are you talking about? Yes, of course, two charts will cover a circle. Choose one as [itex](-\alpha < \theta < \pi+ \alpha)[/itex] and the other [itex](\pi-\alpha < \theta < 2\p+ \alpha )[/itex] where [itex]\alpha[/itex] is some small number.
 
  • #3
i think we are agreed that you can cover a circle with different number of charts but 2 is the minimal number
what you ask is possibly a special way of finding charts.
I guess the method you use is for circle first taking upper half of circle(of course as an open set the end points are not included) than letting any point (x,y) on circle to go (x,0) for example.this gives first chart ,doing same for the lower half gives second one .and for each remaining two points (end points of the half circle) we take a open nhd and suitable hom. So you obtain 4 charts
same method gives for sphere 6 charts but 2 is enough (which is found by different methods.the latter is found by stereographic projection usually)
 

1. What is a coordinate chart?

A coordinate chart is a set of mathematical equations or functions that describe the relationship between points in a particular space. It is often used in geometry and other areas of mathematics to help visualize and understand the properties of different shapes and objects.

2. How do coordinate charts cover a circle?

A coordinate chart can cover a circle by using a set of equations or functions that map points on the circle to points in a two-dimensional coordinate system. By using these equations, every point on the circle can be represented by a unique set of coordinates, allowing the entire circle to be covered.

3. What is the purpose of using coordinate charts to cover a circle?

The purpose of using coordinate charts to cover a circle is to help visualize and understand the properties of the circle in a two-dimensional space. It allows for precise measurements and calculations to be made, which can be useful in various applications, such as engineering and physics.

4. Are there different types of coordinate charts to cover a circle?

Yes, there are different types of coordinate charts that can cover a circle. Some common examples include Cartesian coordinates, polar coordinates, and parametric equations. Each of these coordinate systems has its own set of equations and properties, making them useful in different contexts.

5. What are the advantages of using coordinate charts to cover a circle?

Using coordinate charts to cover a circle has several advantages, including the ability to precisely define and measure points on the circle, the ability to easily visualize the circle in a two-dimensional space, and the ability to perform calculations and solve problems involving the circle. Additionally, coordinate charts can be easily extended to cover other shapes and objects, making them a versatile tool in mathematics and science.

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