Hello,
There is a possible bug with Equation Systems, elements as real numbers and functions.
1. Using the Live version
[LIVE width=170 height=240]http://smath.info/live/?file=885[/LIVE]
2. Using the recent Alpha version.
If the second element was not real (1.2) but integer, sin(s) will not complain.

Try to reproduce, please.
Regards,
Radovan
When Sisyphus climbed to the top of a hill, they said: "Wrong boulder!"