This question may seem like a duplicate, but I haven't seen any satisfactory answer in similar questions.
Is there a way to add a line break in displayed math mode without using multiple-line environments such as gather or eqnarray? I want to display an equation that spans multiple lines inside an equation environment (so that the entire thing only gets one number).
My current code:
\begin{equation}
A_i=A_0-\sum_{j=0}^{i-1}[(2^i\cdot3)\cdot\frac{s_i^2}{18}\cdot sin(\alpha)]=%
\sum_{j=0}^{i-1}[(2^i\cdot3)\cdot\frac{(\frac{s_0}{3^i})^2}{18}\cdot sin(180º-\frac{120º}{2^i})]=%
\sum_{j=0}^{i-1}[(2^i\cdot3)\cdot\ddfrac{s_0^2}{18\cdot3^{2i}}\cdot sin(180º-\frac{120º}{2^i})]
\end{equation}
This "overflows" the line:
I want to add a line break in between (after one of the = signs), but still have the whole thing labelled as (4.7).
