Can I bury RG6 in the same conduit as electric?
No, you cannot. Unless you're not covered by National Electrical Code (or similar), you don't care about following codes, or you're also installing a permanent barrier or listed divider.


  National Electrical Code
  
  Chapter 8 Communications Systems.
  
  Article 820 Community Antenna Television and Radio Distribution Systems.
  
  820.133 Installation of Coaxial Cables and Equipment.
  Beyond the point of grounding, as defined in 820.93, the
  coaxial cable installation shall comply with 820.133(A)
  and (B).
  
  (A) Separation from Other Conductors.
  
  (1) In Raceways, Cable Trays, and Boxes.
  
  (b) Electric Light, Power, Class 1, Non–Power-Limited
  Fire Alarm, and Medium-Power Network-Powered Broadband
  Communications Circuits. Coaxial cable shall not be
  placed in any raceway, compartment, outlet box, junction
  box, or other enclosures with conductors of electric light,
  power, Class 1, non–power-limited fire alarm, or medium-power
  network-powered broadband communications
  circuits.
  
  Exception No. 1: Where all of the conductors of electric
  light, power, Class 1, non–power-limited fire alarm, and
  medium-power network-powered broadband communications
  circuits are separated from all of the coaxial cables by
  a permanent barrier or listed divider.


You can Either put a second conduit in the trench for communications circuits, or put direct-burial coaxial cable in the trench.