This is a good question for a math teacher. I know it can be done but I can't tell you the steps.
My concerns would be best described as analog vs digital.
Do you want to take a sample point every 1% of the line and use straight lines between? This would be the digital version.
The other method that comes to mind is creating an equation and graph in excel, then revision the equation until it matches. In this case the equation would be an up-side down perabola y=f(X^2). I would start with coordinate system in the bottom center, and the two tend points. Create a perabola equation that matches the ends. then play with the variables until the curve matches.
This would be really cool if you could say, display the excel graph on top of the cad view while revising the formula.
And since SE effectively has a spreadsheet, and you can link variables to dimensions. It would be a lot of work, but could be done by programming equation into SE.