asin and acos wrong



> 
> (C5) asin(0.5);
> (D5) 0.5

This is clearly a bug.  Thanks for reporting it.

> The plot of the function shows a really weird function:
> (C8) plot2d(asin(x), [x,-4,4])$

This will give a strange plot if asin is wrong, of course.  But keep in
mind, too, that plot2d only shows the real part of a function.  So if
you had a *correct* implementation of asin, the part between -1<x<1 will
look normal, but for x>1, y=pi/2 and for x<-1, y=-pi/2.  Unfortunately,
there is also a bug in realpart, which gives
ev(realpart(asin(-2.0)),numer) => 4.71 (= 3/2 pi) instead of -pi/2 (bug
#816166).  I will try to fix that for a future release.

> (Maxima 5.9.0 from Debian's package 5.9.0-11)

Could you please include full version information as reported by
build_info()?  I don't know how the Debian package is built (which
version of which Lisp, for example).

     -s