Yes you do need an HDMI cable to hook your 360 to your Optoma GT720 projector, that is the only interface it has that is compatible with an xbox 360. You can get an HDMI cable for a low price though, just $6.99 from the link I have at the bottom of my answer here...
Please make sure you rate my answer 4 thumbs up, it is extremely important to me. I would be forever grateful if you could do so. If you need more help on this question please just respond to my answer here and I will get right back to you.
Answers & Comments
Yes you do need an HDMI cable to hook your 360 to your Optoma GT720 projector, that is the only interface it has that is compatible with an xbox 360. You can get an HDMI cable for a low price though, just $6.99 from the link I have at the bottom of my answer here...
Please make sure you rate my answer 4 thumbs up, it is extremely important to me. I would be forever grateful if you could do so. If you need more help on this question please just respond to my answer here and I will get right back to you.
http://www.amazon.com/gp/product/B001T9NUJE?ie=UTF8&tag=dependascient-20&linkCode=as2&camp=1789&creative=390957&creativeASIN=B001T9NUJE
Thanks
Tim