Connect External monitor in Single user mode

Hi

I just bought a macbook air cheap off the internet as the screen is busted and have connected my macbook air to an external display. Which works fine. However I would like to boot in single user mode and unable to connect the external monitor in this mode. Command F1 doesnt seem to be working. The external monitor does not receive a signal until the login screen. Please help as I do not have the login and would like to reset the password in single user mode