I have a context document with several equations. One really nice feature
with equations is that by default you can search for variable names in
equation in a PDF reader like acrobat. However, I needed to configure the
document to use arial for the text. Once I do this, the equations are no
longer searchable. I assume something happened to the mathematics font. How
to I change the font for the document text, but keep the math equations
searchable? Is there a way to change the document font, but not affect the
math font? Here is a sample of how I configured the font. The equations are
no longer searchable.

% Load the Arial font values for regular, italics, bold, etc.
\starttypescript [serif] [arial]
  \definefontsynonym [Serif]               [name:arial]
  \definefontsynonym [SerifBold]           [name:arialbold]
  \definefontsynonym [SerifItalic]         [name:arialitalic]
  \definefontsynonym [SerifSlanted]        [name:arialitalic]
  \definefontsynonym [SerifBoldItalic]     [name:arialbolditalic]
  \definefontsynonym [SerifBoldSlanted]    [name:arialbolditalic]
  \definefontsynonym [SerifCaps]           [name:arial]
\stoptypescript

% Now we define the 'arial' font as an available option
\definetypeface [arial]    [rm] [serif] [arial]

% Set 'arial' 10pt as the default font for the document
\setupbodyfont [arial,rm,10pt]

\starttext

$z_1 = x_1 + y_1$

$a = b + c$

\stoptext