hyperbolic functions

ada0713

1. The problem statement, all variables and given/known data
The Saint Louis arch can be approximated by using a function of the form y=bcosh(x/a). Putting the origin on the ground in the center of the arch and the y axis upward, find an approximate equation for the arch given the dimenson shown in the figure(attachment). In other words, find a and b


3. The attempt at a solution

my attempt was that since y=bcosh(x/a) is same as

y= b-0.5a(e[tex]^{x/a}[/tex]+e[tex]^{-x/a}[/tex])

I tried to plug in x entercepts and y intercepts and
slove for the unknown, but it got so complicated and I
couldn't find either a or b.
i guess i have to find a different method.
can anyone help?

Attached Images

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