Merge pull request #366 from grahamwhaley/20201119_gui_additions

Minor gui text updates

gui/formulas.tex

+% Generate plain formulas to be turned into png files via a pdf. Code hints taken
+% from:
+%
+% https://tex.stackexchange.com/questions/287481/using-latex-to-generate-png-images-of-an-equation/287501
+%
+\documentclass[multi={mymath},border=1pt]{standalone}
+% \usepackage{amsmath}
+\newenvironment{mymath}{$\displaystyle}{$}
+
+\begin{document}
+
+\begin{mymath}
+  F = Fcenter * 2^{(signal * octaves)}
+\end{mymath}
+
+\end{document}

gui/index.html

 		frequency is:
 	</p>
 	<p>
-		F = Fcenter * 2^<sup>(signal * octaves)</sup>
-		<br><small>If anyone knows how to do HTML equations, please
-		help me improve this.....</small>
+		<img src="img/filter_formula.png">
 	</p>
 	<p>When operating with signal control of corner frequency, this
 		object uses approximately 4% of the CPU time on Teensy 3.1.
 <script type="text/x-red" data-help-name="AudioAnalyzeToneDetect">
 	<h3>Summary</h3>
 	<div class=tooltipinfo>
-	<p>Detect the level of a single tone</p>
+	<p>Detect the level of a single tone.</p>
+	<p>Uses the
+	<a href="https://en.wikipedia.org/wiki/Goertzel_algorithm" target="_blank">Goertzel algorithm</a>
+	.</p>
 	</div>
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>