Correct format of an equation

Question

I have this equation:

\begin{equation}
B_{1} = 0.9(B_{2})  + \\ 
\bigg[ 
   \sqrt{(x_{1}^2 + y_{1}^2 + z_{1}^2)}-\sqrt{(x_{2}^2 + y_{2}^2 + z_{2}^2)} 
\bigg] 
\end{equation}

I heard the B_{1} is some kind of result (like a sum, product, etc.) and must be declared as such, so TeX applies the math style guide - correct appearance on it.

But I dont know what it is and how to mark it. Which command can I use here?

Answer 1

You can't have a line break in an equation environment, so the \\ does nothing.

A better way to type the equation could be

\begin{equation}
B_{1} = 0.9\,B_{2} + \Bigl[
        \sqrt{(x_{1}^2 + y_{1}^2 + z_{1}^2)}-
        \sqrt{(x_{2}^2 + y_{2}^2 + z_{2}^2)} \; \Bigr] 
\end{equation}

so that the various components of the equation are more visible.

I've made a couple of changes:

• \Bigl[ for the opening bracket and \Bigr] for the closing one (as \bigg size seems too much). Notice the final l or r to declare the type of delimiter;

• a thin space \, between the decimal number 0.9 and B_{2} (which I wouldn't put in parentheses), as the result of 0.9B_{2} might be confusing;

• a thick space between the second square root and the closing bracket for symmetry with the space at the start.

There is no special way to mark B_{1}: it's just a symbol with a subscript.