You are doing things correctly. You just need to install some fonts.
See
http://wiki.sagemath.org/faq#IgetanerrorfromjsMathorthemathsymbolsdon.27tlookrightwhendisplayinginthenotebook
Typically, you could do show(M) if M is a matrix and it will show the
thing in a nice format.
Jason
I am getting the same error, so I followed up the wiki and I installed
both jsmath-fonts and smath-fonts-sprite packages in Ubuntu, but the
error still stays...
Ondrej
It wouldn't be hard to change. Davide gave us instructions a long time
ago on the mailing list to do something like this, IIRC.
Jason
I think this error is very annoying, as I am getting it on basically
all computers where I tried it.
When I get some time, I'll try to figure out how to patch jsmath not
to show this message at all.
Ondrej
Install the jsmath-image-fonts spkg (i.e., *sage* package, not ubuntu
package), and the error should go away...I think...
That said, I agree that the error message is annoying, though it's
probably annoying for a reason...
Jason
Ah -- I was stupid, yes, this fixes the problem! Thanks a lot!
>
> That said, I agree that the error message is annoying, though it's
> probably annoying for a reason...
So maybe jsmath-image-fonts could be in Sage by default?
Ondrej
It's too big---something like 80MB unzipped (lots and lots and lots of
little tiny image files; one for each character).
The error message should be changed, and we ought to distribute the
fonts from the jsmath homepage with Sage, so that instead of an error
message, there is a nice helpful link that says something like "to get
much better fonts, click here and follow these instructions, or install
the jsmath-image-fonts spkg"
Jason
+1!! We've been meaning to do that forever...
William