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

    MTH$SINCOS, MTH$DSINCOS, MTH$GSINCOS, and MTH$HSINCOS return the
    sine and cosine of the input angle by reference in the sine and
    cosine arguments.