ArcCosh[z] == (Sqrt[z - 1]/Sqrt[1 - z]) (Pi/2 - (z Sqrt[1 - z^2])/ (1 - (1 2 z^2)/(3 - (1 2 z^2)/(5 - (3 4 z^2)/ (7 - (3 4 z^2)/(9 - (5 6 z^2)/(11 - \[Ellipsis]))))))) /; !IntervalMemberQ[Interval[{-Infinity, -1}], z] && !IntervalMemberQ[Interval[{1, Infinity}], z]

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2001-10-29