hyperbolic function catenary problem

An electric cable strung between supporting posts, takes the form of the following curve, which is called a
catenary, and which has the following relationship:
𝑦 = a cosh (𝑑/2a)

a = minimum height above the ground of the cable
d = distance between the supporting posts
(i) If the height of the posts is 10 m and the minimum height of the cable above the ground is
8 m, determine the distance between the posts.
(ii) Determine the length of the cable s, between the posts in (i) above, given by the following
equation:
𝑠 = 2a sinh ( 𝑑/2a)

the formula y = a cosh (d/2a) will only have a single value for y.... is there something missing ?

https://media.cheggcdn.com/study/5f3/5f3b4ac0-588f-449e-854b-c27215a6b1c9/image
y would be the height of the support posts a distance d apart, so its not really a curve ... Though it sort of is if you regard d as a variable and not related to the support posts ...

Thanks for this. I've been overthinking it

Are you ok with it now? It should just be a couple of lines.

Thanks for this. I've been overthinking it

the formula y = a cosh (d/2a) will only have a single value for y.... is there something missing ?