*s(t)*=$\int_{t_0}^{t}\left | R'(\xi) \right | d\xi$ What is $\xi$ ?

[Kuhan]

s(t)=\int_{t_0}^{t}\left | R'(\xi) \right | d\xi
What is \xi ?

In the above arc length formula with $\xi$, what is $\xi$?

 

[Kuhan]

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[micromass]

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