I've been trying to make the integral symbol "upright", meaning I want it not to be slanted, as in Born's Principles of Optics 7th edition. I've tried the \varint
of the wasysym
package, but it appears not to be automatically resized.
Can someone help me with this? Thank you for your attention and patience.
Per @Mico's suggestion, here's the preamble of my document:
\documentclass{book}
\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{fancyhdr}
\usepackage{english}{}
\usepackage{amsthm}
\usepackage{xfrac}
\usepackage{makeidx}
\usepackage{physics}
\usepackage{commath}
\usepackage[toc,page]{appendix}
\usepackage{english}
, do please use\usepackage[english]{babel}
.