# Is it possible to reprint an equation without actually rewriting it? [duplicate]

I have an equation like:

$$\label{whatever} x+y=1$$


I want to write it again, keeping the same number. I know I could do the following:

$$x+y=1 \tag{\ref{whatever}}$$


However, I would like to get the same outcome without rewriting the full equation. The reason is that I may change the first equation, and I would like the change to be automatically applied to all the cases in which the equation is repeated. I.e. I'd like to have something like

$$\rewrite{whatever} \tag{\ref{whatever}}$$


Is it possible?

• Related: Recalling a theorem – Werner May 16 '13 at 19:19
• why not just define the equation code as a named macro? you'd still have to label and tag it separately, but the contents would have to be written only once. – barbara beeton May 16 '13 at 19:20
• – cgnieder May 16 '13 at 19:23