I program scripts in <A HREF="https://maxima.sourceforge.io/">maxima</A> (wxmaxima), a computer algebra system.

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Book with examples: 
<ul>
<li> Timberlake, Todd Keene, and J. Wilson Mixon. Classical mechanics with maxima. Springer New York, 2016.
</ul>



Some useful tips
<ul>

<li>There are on internet some "Maxima online" web sites which run maxima scripts.
  

<li>quote-quote operator forces Maxima to evaluate:

<pre>
f(x):=cos(x)+sin(x);
derivative(f(x),x,1);
fprime(x):=''%;
</pre>
defines fprime(x):= cos(x) - sin(x);

<li>single-quote operator forces Maxima to recognize the command but not to evaluate it:
<pre>
theta(mu,sigma):=mu/sigma**2;
'theta(1,2);
theta(1,2);
</pre>
gives theta(1, 2) and 1/4
</ul>