Double threats: Musicians who act

POSTED: 10:56 PM PDT Sep 29, 2013    UPDATED: 11:00 PM PDT Jun 24, 2015 
Rihanna in Battleship

For some singing stars, dominating the music world just wasn't enough. From Frank Sinatra to Rihanna, take a look at musicians who have tried their hands -- with varying success -- at acting.