Chain fixed at two points, how far does it drop down? Not too sure whether this should be in maths or physics, but oh well.
If you have a metal chain of length h metres
and you have 2 points, the distance between them being x metres,
If h is less than x, then the chain will obviously not fit between the 2 points.
If h=x, then the chain will just about be able to be attached to the points, and it will make a straight line between the 2 points.
My question is that when h>x, if one attached the chain to the points, the chain would obviously dip and a parabola shaped curve would be seen.
What would the distance between the midpoint of the chain and midpoint of the 2 points be, and also what would the angle between the tangent of the chain and the straight line between the 2 points be? Sorry that there's no diagram. 
I'm guessing this is a trig question?

Hint.
One can prove that the curve that will fit your chain is a catenary.
Based on that, you can find the parameter $a$ of the catenary in order to have its length equal to $h$ knowing the distance $x$ between the two points. You will then be able to compute the height of the drop down.
