PLEASE HELP I HAVE BEEN STUCK ON THIS FOR OVER AN HOUR!!!!!!!
Telephone wire hangs between two poles at x=-b and x=b. It takes the shape of a catenary with equation y=c+acosh(x/a). From this I found that the length of the wire is 2asinh(x/a).
Suppose two telephone poles are 50 ft apart and the length of the wire between the poles is 51 ft. If the lowest point of the wire must be 20 ft above the ground how high up on each pole should the wire be attached?

Question

PLEASE HELP I HAVE BEEN STUCK ON THIS FOR OVER AN HOUR!!!!!!!
Telephone wire hangs between two poles at x=-b and x=b. It takes the shape of a catenary with equation y=c+acosh(x/a). From this I found that the length of the wire is 2asinh(x/a). 
Suppose two telephone poles are 50 ft apart and the length of the wire between the poles is 51 ft. If the lowest point of the wire must be 20 ft above the ground how high up on each pole should the wire be attached?

anonymous · Answer

c+a=20

anonymous · Answer

I also think you can set up as 2asinh(x/a)=51

anonymous · Answer

I don't know where to go from here though.