Don't need too much help here, just a bit of clarification.

Suppose I have to find the arclength parametrization of t --> (cost,sint,cosht) : [-pi,pi] --> R^3 .

I take the norm of the derivitive of the function which ends up as cosh(t) and integrate it. Do I integrate cosh(s)ds (random dummy variable) with upper limit t and lower limit 0, or upper limit t and lower limit -pi ?

Unfortunately our notes don't explain the choice of limits.

Thanks.