Epson 73c - Manual (Page 30)

24 Using the Projector
If you’re using a Macintosh laptop with OS X:
You may need to set up your system to display on the projector screen
as well as the LCD screen. Follow these steps:
1. From the Apple menu, select System Preferences , then click
Displays.
2. Select VGA Display or Color LCD , click Arrange or
Arrangement , and make sure Mirror Displays is checked.
Click here
Select Mirror
Displays