Modelling the Shape of St. Louis Arch

This GeoGebra dynamic worksheet is to determine whether the shape of St. Louis Arch can be modelled by a quadratic function.
1. Drag the three sliders to vary the values of a, b and c. 2. Try to fit a curve for the inner and outer arches of St. Louis Arch. 3. Can the shape of St. Louis Arch be modelled by a quadratic function? 4. What other objects in our daily life can be modelled by a quadratic function? Check your claim with the help of GeoGebra.