/sys$common/syshlp/helplib.hlb RTL Routines, MTH$, MTH$xACOSD, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 cosine

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

    Cosine of the angle whose value (in degrees) is to be returned.
    The cosine argument is the address of a floating-point number
    that is this cosine. The absolute value of cosine must be less
    than or equal to 1. For MTH$ACOSD, cosine specifies an F-floating
    number. For MTH$DACOSD, cosine specifies a D-floating number. For
    MTH$GACOSD, cosine specifies a G-floating number.