tremolo question; don't understand how to apply the manual to my situation

[Kenneth Wolcott]

Hi;

  I have a tremolo question.

  4/4 time
  bass clef (piano part)
  polyphony apparently required
  two half notes, the first half note is in both voices

  I don't understand the tremolo repeat section in the manual, and
definitely not when it comes to this situation.  See attached
screenshot.

  Here's my code (without the tremolo) for this measure (bass clef only):

  <<
    { e,2 e | } % tremolo??
  \\
    { e,2 ~ e,4 r | }
  >>     % m17

Thanks,
Ken Wolcott