keep an eye on the blue line while move it to 45° or to 145°. While moving if the line flickers or you see line vanished then its the cable that connects your display to your graphic card. If it remains same then its the screen of your laptop, it should be replaced.
Can you type down the name and the model of laptop? (written normally on a slab located at the base of the laptop)
You are trying well to help for trouble shooting!!