# Correct way to align equations equal to zero

This is a question related to formatting. I have an expression that is equal to zero; I work over this expression to obtain a final relation as shown below:

\begin{align*} 0 & =\int_{V}\nabla\cdot\mathbf{A}\,\mathrm{d}V\\ & =\int_{S}\mathbf{A}\cdot d\mathbf{S}\\ & =\int_{S}\mathbf{\hat{n}}\cdot\mathbf{A}\,d\mathit{S}\\ & =\left(\mathbf{A}_{i}-\mathbf{A}_{e}\right)\cdot\mathbf{\hat{n}} \end{align*}

My question is: is it correct formatting to leave the zero in the left hand side? I have searched for answers but I could not find it. Thanks in advance.

• I see nothing wrong with that. – MSDG Dec 7 '18 at 16:04
• I've seen many such calculations. The only other way to format it that would look natural to me would be to reverse the entire calculation, starting with $\left(\mathbf{A}_{i}-\mathbf{A}_{e}\right)\cdot\mathbf{\hat{n}}$ and concluding with $0$. But if the natural flow of your argument in its context runs the direction you've shown, there is nothing wrong with it. – Paul Sinclair Dec 8 '18 at 2:42
• That looks correct to me, but... I feel like this question should be on Meta instead. On the other hand, the notation tag description does mention usage... – Robert Soupe Dec 8 '18 at 2:47
• Thanks for your responses! This was very helful ! – nodarkside Dec 8 '18 at 2:51