Angle and trig definitions in curved space

In summary, the conversation discusses the concept of pi being constant or changing in curved space and how this affects other mathematical formulas and concepts such as sine waves. It is clarified that pi has a specific value and definition, but in non-Euclidean geometries, this value may be different or not constant.
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newjerseyrunner
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I was going to ask a question about whether or not pi was constant or changed with curved space. I found the answer on here that it does indeed change. Then I started thinking about the ramifications of that. sine waves are dependent on pi, so they should change too. Does sin(theta) = opposite / hypotenuse still hold true for all spaces?
 
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Just to clarify... ##\pi=4\arctan(1)=3.1415...##
It's a particularly interesting number, which is also equal to the circumference/diameter ratio of any circle on a Euclidean plane.
Now in a curved space, the circumference/diameter ratio is no longer independent of the circle... and many formulas that work for (say) triangles in the plane don't work any more. [You must do calculus and differential geometry now.]
However, at any point in a curved space, there is a tangent vector space there. On a Euclidean plane in that vector space, that ratio is still ##\pi## for any circle drawn on it.
 
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newjerseyrunner said:
I was going to ask a question about whether or not pi was constant or changed with curved space. I found the answer on here that it does indeed change. Then I started thinking about the ramifications of that. sine waves are dependent on pi, so they should change too. Does sin(theta) = opposite / hypotenuse still hold true for all spaces?
You may be talking about something other than "[itex]\pi[/itex]". [itex]\pi[/itex] has a very specific value. There are a number of different ways to define [itex]\pi[/itex], one of them being the ratio between the circumference of a circle divided by the diameter of that circle in Euclidean Geometry. In a variety of forms of non-Euclidean geometries, that ratio might be something other than [itex]\pi[/itex] or the ratio might not be a constant. That has nothing to do with the number [itex]\pi[/itex].
 

Related to Angle and trig definitions in curved space

1. What is the difference between angle and arc length in curved space?

In curved space, angle and arc length are not equivalent concepts. Unlike in Euclidean space where an angle is defined as the ratio of arc length to the radius of a circle, in curved space, the angle is determined by the curvature of the space itself. This means that two curves with the same arc length can have different angles in curved space.

2. How do we measure angles in curved space?

In curved space, we use a mathematical concept called a geodesic to measure angles. Geodesics are the shortest paths between two points on a curved surface, and they follow the curvature of the space. The angle between two geodesics is the angle in curved space.

3. Can we use trigonometric functions in curved space?

Yes, we can use trigonometric functions in curved space, but they are not the same as the traditional trigonometric functions used in Euclidean space. In curved space, the trigonometric functions are defined in terms of the geodesic distance between points, rather than the straight-line distance.

4. How does the curvature of space affect trigonometry?

The curvature of space affects trigonometry by changing the relationships between angles and sides of a triangle. In Euclidean space, the sum of the angles in a triangle is always 180 degrees, but in curved space, the sum can be greater or less than 180 degrees depending on the curvature of the space. This means that trigonometric identities and formulas also change in curved space.

5. Can we apply Euclidean trigonometry in curved space?

No, we cannot apply Euclidean trigonometry directly in curved space. Euclidean trigonometry is based on the assumption of a flat, two-dimensional space, while curved space has a non-zero curvature. This means that the formulas and concepts of Euclidean trigonometry do not hold true in curved space.

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