Math mode questions on font size

amsmathmath-mode

I've been using $$ \nabla $$ on StackExchange to inline multiple math equations with success. I'm switching to pure Latex using Overleaf and have questions.

My goal is to produce a document with some simple left aligned or centered equations. I try the following code, however it has problems:

  1. Font size too small of math equations, changing \documentclass[Xpt]{article} has no effect on math equation font size
  2. Spacing between each equation line is too small. I want to increase the spacing

Can anyone provide suggestions here? I provide some sample code I'm working with:

\documentclass{article}
\usepackage{graphicx} % Required for inserting images
\usepackage{amsmath}

\begin{document}
\begin{math}
     C_x(...) = \sum_{j=0}^{n_L - 1} (a_j^{(L)} - y_j)^2 \\
     a_j^{(L)} = \sigma(z_j^{(L)}), z_j^{(L)} = \sum_{k=0}^{n_L - 1} (w_{jk}^{(L)} a_k^{(L-1)}) + b_j^{(L)} \\
\end{math}

\end{document}

Best Answer

I suggest you display the equations across three lines, rather than just two. To increase the vertical spacing between the rows, append [\jot] to \\.

A suggestion about notation (not implemented in the code below): Would it be ok to replace all instances of (L) and (L-1) with just L and L-1, respectively? Making this change would greatly reduce the high degree of visual clutter.

The code shown below doesn't specify a font size option when executing the \documentclass directive, implying that the default 10pt document font size is employed. If you choose to set 12pt as one of the document class options, the text and math fonts will be increased linearly by 20 percent relative to the default 10pt option.

enter image description here

\documentclass{article}
\usepackage{amsmath} % for `align*` env.

\begin{document}

\begin{align*}
C_x({}\cdot{}) &= \sum_{j=0}^{n_L - 1} \bigl(a_j^{(L)} - y_j \bigr)^2 \\[\jot]
     a_j^{(L)} &= \sigma\bigl(z_j^{(L)}\bigr) \\[\jot]
     z_j^{(L)} &= \sum_{k=0}^{n_L - 1} w_{jk}^{(L)} a_k^{(L-1)} + b_j^{(L)} 
\end{align*}

\end{document}
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