Parameterizing Paths: Understanding the Solution to a Twin Paradox Problem

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In summary, the conversation discusses a solution to question 4 on a document regarding the twin paradox inequality and proper time of a path. The person is confused about how the vectors A, B, and C were chosen and how the paths c1, c2, and c3 were parametrized. The expert summarizer explains that the choice of vectors and parametrization does not affect the final result, as the integral will give the same length regardless. They also mention the use of the parametrization formula for a line from point A to B, where (1-l) represents the direction.
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Kuma
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Homework Statement



Hi, I'm just seeking an explanation of this solution for question 4 on the following document.

https://docs.google.com/viewer?a=v&...Sg3wEk&sig=AHIEtbSrlOPM8RXfN8I7gBoTxzXwVzwddg


I'm just wondering how did they just pick out the vectors A, B and C arbitrarily? And I'm more confused about how they parametrized the paths c1, c2 and c3. Why choose (1-λ)?
 
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What you have to calculate is the length of paths which are all geometric object. So no matter how to parametrize them (pick out vector in this case) the integral will give you the same result (the length).
And if you use the fact that given two points A and B you can find the parametrization of a line from A to B by c(l) = A + (B-A)*l (l=0 to 1 and B-A give you direction) then you can rewrite this as c(l) = (1-l)*A + l*B and this is where (1-l) came in.
 

1. What does it mean to parameterize a path?

Parameterizing a path means representing the path as a function with a set of variables, usually denoted by t, that can take on different values to trace out the path.

2. Why is it important to parameterize a path?

Parameterizing a path allows for easier manipulation and calculation of the path, as well as the ability to generalize the path to different scenarios.

3. How do you parameterize a path?

To parameterize a path, you need to express the coordinates of the path as a function of a parameter. For example, for a path in the xy-plane, the coordinates could be expressed as x(t) and y(t), where t is the parameter.

4. What are some examples of parameterizing a path?

Some examples of parameterizing a path include expressing a straight line as x(t) = mt + b, where m is the slope and b is the y-intercept, or a circle as x(t) = rcos(t) and y(t) = rsin(t), where r is the radius.

5. How is parameterizing a path related to vector-valued functions?

Parameterizing a path is closely related to vector-valued functions, as the function that represents the path is usually a vector function. The vector function takes in the parameter and outputs a vector that corresponds to a point on the path.

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