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

 angle-in-radians

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

    The angle in radians. The angle-in-radians argument is the
    address of a floating-point number. For MTH$COS, angle-in-radians
    is an F-floating number. For MTH$DCOS, angle-in-radians specifies
    a D-floating number. For MTH$GCOS, angle-in-radians specifies a
    G-floating number.