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

    OpenVMS usage:floating_point
    type:         F_floating, D_floating, G_floating
    access:       write only
    mechanism:    by value

    The hyperbolic cosine of the input value  floating-point-input-
    value. MTH$COSH returns an F-floating number. MTH$DCOSH returns a
    D-floating number. MTH$GCOSH returns a G-floating number.