VMS Help RTL Routines, MTH$, MTH$xATANH, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 hyperbolic-tangent

    OpenVMS usage:floating_point
    type:         F_floating, D_floating, G_floating
    access:       read only
    mechanism:    by reference

    Hyperbolic tangent of an angle. The hyperbolic-tangent argument
    is the address of a floating-point number that is this hyperbolic
    tangent. For MTH$ATANH, hyperbolic-tangent specifies an F-
    floating number. For MTH$DATANH, hyperbolic-tangent specifies
    a D-floating number. For MTH$GATANH, hyperbolic-tangent specifies
    a G-floating number.