If I compile this code in my system (Windows 10, Miktex 2.9, Tikz 3.01a) everything is fine except that the rotated formulas are shifted to the right so that the bottom one straddles the right side of the box. If I change the measure (text width) from 5.5 to 5 the output is as it should (or very nearly so); it seems this type of thing never happens; it is rather disturbing; is there a known explanation for that? What's current knowledge regarding this sort of discrepancy?
The code is repeated below.
\documentclass{article}
\usepackage[landscape,margin=0cm]{geometry}
\usepackage{mathtools}
\usepackage{amssymb,amsthm}
\usepackage{multicol}
\usepackage[most]{tcolorbox}
\usepackage{tikz}
\usetikzlibrary{positioning}
\newtcolorbox{mybox}[2][]{width=\linewidth,fontupper=\scriptsize,
fonttitle=\bfseries\sffamily\scriptsize, colbacktitle=black, enhanced,
attach boxed title to top left={yshift=-2mm,xshift=3mm},
boxed title style={sharp corners},top=2mm, bottom=1mm, left=1.5mm,
right=1.5mm, title=#2, colback=white}
\pagestyle{empty}
\parindent=0pt
\parskip=2pt
\begin{document}
\begin{multicols*}{3}
\begin{mybox}{Single Side-Band (SSB)}
\begin{tikzpicture}[node distance=2mm, inner sep=0pt, outer sep=0pt]
\node (image) {\includegraphics[width=3.4cm]{example-image-a}};
\node (phase) [align=center, text width=5.5cm, right=of image.north east,
anchor=north west] {
Phase Shifting method: \\
$\phi_{SSB} = A_{c}[m(t)\cos 2\pi f_{c}t\mp\hat{m}(t)\sin2\pi f_{c}t]$
};
\node [below=of image.south west, anchor=north west,text width=7.5cm] {
Demod of SSB-SC: \\
\quad$=A_{c}m(t)+\underbrace{A_{c}[m(t)\cos 4\pi f_{c}t\mp \hat{m}(t)\sin4\pi f_{c}t]}_{\text{Suppressed by LPF}}$};
\node [rotate=90, text width=8cm, below=of phase.south east, anchor=south
east, font=\tiny] {
\begin{align*}
\phi_{SSB} = & A_{c}[m(t)\cos 2\pi f_{c}t\mp\hat{m}(t)\sin2\pi f_{c}t] + A\cos2\pi f_{c}t, \\
= & E(t)\cos(2\pi f_{c}t + \theta(t)) \\
\text{where}\quad E(t) = & A_{c}\sqrt{[A+m(t)]^{2} + [\hat{m}(t)]^{2}} \text{ and } \theta(t)=-\tan^{-1}\left\{ \frac{\hat{m}(t)}{A + m(t)} \right\}
\end{align*}
};
\end{tikzpicture}
\end{mybox}
\end{multicols*}
\end{document}
\listfilesthe most recently updated files are thel3kernelones updated on 2018/09/24. I run debian testing, so my files lag a little behind the latest. Could outdated files on my machine be the causing problems? – David Purton Nov 03 '18 at 12:36