/ x\ acos\E /
acos(E^x)
x -e ------------- __________ / 2*x \/ 1 - e
/ 4*x 2*x \ | 3*e 4*e | x -|1 + ----------- + --------|*e | 2 2*x| | / 2*x\ 1 - e | \ \1 - e / / --------------------------------- __________ / 2*x \/ 1 - e