Using line equations to determine a height in a 2D plane

[RobertWK]

I have a sheet which shows me approximate equations for half of the height of an ellipse.

However the distances rely on three variables, which I cannot use in the equation line tool; they can only be x(t), y(t) in my case.

Does anyone have any recommendations?

[johnsonshiue]

Do you mind sharing the equation here or sending it to me directly (johnson.shiue@autodesk.com)?

Thanks!