[Tex/LaTex] Big \sum instead of small \sum in array environment


\min \: A = \min \: \sum_{i\in B} C_i 
\\ \\
\min \: D = \min \: \sum_{i\in B} \pi_i \cdot F_i

image of the equation
How can I get i \in B below the \sum symbol without breaking the align into multiple aligns?

Best Answer

By putting a \displaystyle in front of the \sum. You basically want the font to behave like it does in a top-level environment, because it's nested in an array it gets assigned a \textstyle font size.

Why you're not aligning the equations on the equals sign beats me though. It might be better to use two equation environments in this case, the code wouldn't look so bloated as it does now.