Where can I find programs/apps like the person in this Youtube video is using: https://www.youtube.com/watch?v=FKvnmxte98A
I don't even know how they're called so I'm not sure how to search for them.
Basically I need the app to draw electrical circuits, and if possible, be able to use it to write mathematical equations.
I also need to be a free/open source.
Platform: Microsoft Windows