[OS X TeX] `amsmath.sty' not found

[Antonio]

I'm trying to use LateXrender, a PHP script that produces an image  
from LateX imput on Web forms.
This solution on my site does not seems to work and in the .log  
generated by LateX there is a message:

! LaTeX Error: File `amsmath.sty' not found.

I have installed LateX-base on a BSD Operating System. Is this  
package outside the base configuration of LateX?
How can I install the missing Package? Thanks ina dvance for your help.

(This is not a proper MacTex question, but I hope you can help me)


------------------------- Helpful Info -------------------------
Mac-TeX Website: http://www.esm.psu.edu/mac-tex/
TeX FAQ: http://www.tex.ac.uk/faq
List Archive: http://tug.org/pipermail/macostex-archives/
List Reminders & Etiquette: http://www.esm.psu.edu/mac-tex/list/