# Vertical spaces around display math [duplicate]

(First of all, I know that  should be used instead of  and I do it.)

I'd like to know about the vertical spacing around math display blocks.

According to texdef -t latex $ we have \[: macro:->\relax \ifmmode \@badmath \else \ifvmode \nointerlineskip \makebox [.6\linewidth ]{}\fi \fi  and texdef -t latex$ returns

\]:
macro:->\relax \ifmmode \ifinner \@badmath \else $$\fi \else \@badmath \fi \ignorespaces  So I didn't see any command for vertical spacing. Since the command $$ appears in the code above I tried also texdef -t tex $$ and texdef -t latex$$ with no success.

If I'm not wrong I remember something related with \abovedisplayskip or something similar.

Well, my question is: Are the vertical spaces above and below the command  the same as the ones inserted by \begin{equation}\end{equation} (and its stared versions)? How to check this reading the macros and codes?