What Does the Parameter 'a' Represent in the Catenary Equation?

[Moonflower]

What are good sources to find a model for catenary used to build suspension bridges?
I know that the equation for catenary is a*sin(x/a). what does a stand for?

Thanks.

 

[lanedance]

have a look at:
http://en.wikipedia.org/wiki/Catenary

i don't think that equation is the correct one for a catenary, but the a is just a constant