There's something I don't get about Equation Driven Curves.  Making the curves is straight forward.  But if the curve is not fixed and someone drags it in space, the equation is no longer valid.  In the below example, this is after I dragged the endpoints up and down.  Clearly in the context of the sketch's coordinate systems, y is not equal to COS(x).  It's as if the curve has its own coordinate system after you drag it.

I see this as a huge liability.  If I get a sketch from someone else, how do I know that they didn't wrongly manipulate the curve and that it's valid in the context of the sketch's coordinate system?

How does not correct this?