Interface FunctionPlotDatumDerivative

The derivative of the parent data fn

Additional information available during function evaluation

True to compute the tangent line by evaluating derivative.fn with the current mouse position (i.e. let x0 be the abscissa of the mouse position transformed to local coordinates, the tangent line to the point x0, fn(x0))

The abscissa of the point which belongs to the curve represented by fn whose tangent will be computed (i.e. the tangent line to the point x0, fn(x0))