Hi all.

I have managed to derive the equation of a catenary from an initial set up. Using calculus of variations and lagrange multipliers. However I have become stuck on finding some remaining constants.

The equation I have at the moment is:

y=(lambda)+Acosh(x/A)

I need to find lambda and A in terms of the length of the chain, L, and possibly the end points of the chain. (-d,0) and (d,0)

I have tried using the integral form of an arc length equal to L, but I can't see how to solve for A, with it being in the argument of cosh, and multiplying it.

Many thanks for any help you can give