I was trying to solve this calculus exercise:
The Saint Louis arch can be approximated by using a function of the form $y=b-a\mathrm{cosh}(x/a)$. Putting the origin on the ground and in the center of the arch and the $y$-axis upward, find an approximate equation for the arch given these dimensions: height 615 and width 530. (in other words find $a$ and $b$).
Now from these data I got two equations:
$b-a=615$
$b-a\mathrm{cosh}(265/a)=0$
but I have no idea how to solve this system. Could you help me?
(that's not homework)