[Maxima-bugs] [maxima:bugs] Re: #3896 Problem with trigreduce

[Stavros M. <mac...@us...>]

Another workaround is 
~~~~
map('trigreduce,cos(1/2*acos(q))^2*sin(1/2*acos(q))^2)
    => (1-q)*(1+q)/4
~~~~
but of course that doesn't fix the bug.


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**[bugs:#3896] Problem with trigreduce**

**Status:** open
**Group:** None
**Labels:** trigreduce 
**Created:** Fri Dec 03, 2021 05:49 PM UTC by Dominik Reitzle
**Last Updated:** Sun Oct 12, 2025 09:32 PM UTC
**Owner:** nobody


I stumbled upon the following problem in trigreduce():
~~~
Maxima 5.45.1 https://maxima.sourceforge.io
using Lisp SBCL 1.4.9
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) trigreduce(cos(1/2*acos(q))^2*sin(1/2*acos(q))^2);

Maxima encountered a Lisp error:

 The value
   1
 is not of type
   LIST

Automatically continuing.
To enable the Lisp debugger set *debugger-hook* to nil.
(%i2) build_info();
(%o2) 
Maxima version: "5.45.1"
Maxima build date: "2021-11-01 10:49:25"
Host type: "x86_64-pc-linux-gnu"
Lisp implementation type: "SBCL"
Lisp implementation version: "1.4.9"
User dir: "/home/rifleman/.maxima"
Temp dir: "/tmp"
Object dir: "/home/rifleman/.maxima/binary/5_45_1/sbcl/1_4_9"
Frontend: false
~~~

The correct answer should be something like (1-q^2)/4 .


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