Do not solve the problem just look at the picture. http://i208.photobucket.com/albums/bb33/DanusMax/giro2_zps11d2056b.jpg Well its the end of the semester and I found out that I had only one of the required books for my undergraduate course. Anyways back to the question. As you can see in the photo what I would like to know is what ψ_0(x)= <x|0>. stands for? I haven't seen examples of how to use it or anything. I do know that it can be broken up and something can be placed in the center <x|?|0>. what i don't know is what that x is or why there's a zero on the other side. What does it mean I would like to have examples if possible.