Does the Subscript x=0 Indicate a Zero x-Component in Vector Notation?

[Bizkit]

I have a quick question to ask you guys. In the first problem found http://whites.sdsmt.edu/classes/ee382/homework/382Homework4.pdf" , does the vertical line with the subscript x = 0 mean that the x-component of the vector is always 0? If so, then I could just remove the x-component from the vector so it would become \vec{\boldsymbol{D}}_{1} = \hat{\boldsymbol{a}}_{y}\beta + \hat{\boldsymbol{a}}_{z}\gamma right? I know this is a really simple question, but since I haven't seen this notation used in a while, I wanted to make sure I knew what it meant.

 

[thebigstar25]

no i don't think so .. it means that equation is equal to the one written when x=0 (at a point x=0) , you can't say that the x-component is zero! If that component for example equal a constant not including x ifself or any combination of other variables , does that necessary lead to a zero of the x-component? ..

Im not going to say I am 100% sure, but that what I think .. I hope that other members reply and comment on that part ..