c1 + c*acosh(x)
c ------------ _________ / 2 \/ -1 + x
-c*x ------------ 3/2 / 2\ \-1 + x /
/ 2 \ | 3*x | c*|-1 + -------| | 2| \ -1 + x / ---------------- 3/2 / 2\ \-1 + x /