If you can check the monitor with another computer or laptop will tell you if it is the monitor.
don't even need to do that. when you unplug most monitors from the back of the PC. most monitors display a logo when you first turn the monitor on or display a no signal graphic on the screen when the monitor id not connected to anything or the monitor is on the but the computer is off. so if you see a line with either of these options it is definitely the monitor