Mathematical Notation in Email

I sometimes use email to communicate with researchers and engineers for mathematical discussion. Then, I always have a problem of writing mathematical notation.  How do you write, for example, the following equation in email?

A nice web page suggests to write

lim{x->0}sin(x)/x  =  1

This is an unambiguous expression. Alternatively, you can use "LaTeX" commands:

\lim_{x\rigtharrow 0}\sin(x)/x = 1

How about the following?

I suggest to use "matlab like" expression:

inv([a,b;c,d]) = 1/(ad-bc)[d,-b;-c,a]

This wil be unambiguous if the other person also knows matlab commands.

If you want to write so complicated mathematical expression as those in the cubic formula, I suggest to make a PDF file and just attach it!