Look at/have similar angle check?

I’m trying to make a very simple openable door for a firstperson game. If the player stands in front of the door, the game needs to check if the player is looking at the door before it can accept player input to actually open it. So far I’ve only found tutorials for something similar, but they never check if the player is actually looking at the door. I know it’s about either doing a trace or checking whether the player has a similar angle with the door’s triggerbox.

Any help/examples on this?