Am 09.05.2015 um 13:46 schrieb Hans Hagen <pragma@wxs.nl>:

On 5/9/2015 2:03 AM, Aditya Mahajan wrote:

Hi,

There is a question on TeX.SX asking how to change the font of \sin,
\cos, etc.

http://tex.stackexchange.com/q/243893/323

I looked at the code, and there does not appear to be an easy solution.
The \mathfunctionlabeltext command has \mathupright hard coded.

One option is to keep this configurable using \setupmathematics, perhaps
mfunction=(normal|italic|sans).

In any case, I think that the current implementation is a bug. The
default font for mathfunctionlabeltext should be typeset in the bodyfont.

this is evil (as it's unpredictable, so no support for side effects):

% \prependtoks \rm \to \everymathematics