building own kinematic: joint dependency syntax?

Hello!
I am attempting to build an own kinemtatic (which I'm quite familiar with basically) which contains multiple joints and some joints should be dependent on another joint.
The "kinemtic builder" offers using a "formula" to express the dependancy. But I can't find any source of how the formula has to be stated, which syntax I need to obeye nor the available functions (I'd need "sinus" "cosinus" "tangens" as well as "power" and "square root").
Can anyone help me?
Thx - BR