How do you get maxima to "simplify" expressions like cos(2*%pi/5)?

Viktor T. Toth wrote:

> Try load(ntrig). Note that unless you're using the latest CVS, it may not
> always give you the correct result outside the first quadrant, due to a sign
> error.

Thanks, that is an interesting coincidence that you had been recently
fixing this little piece of code only a short time before I posted about
this problem.

I didn't know it was something that had received such a specific
treatment.  I wonder if there was some way I should have thought
to come across this without having to ask.