Your biologist friend is investigating the shape of a plant structure.

It can be modelled as a surface whose cross-section parallel to the-plane is a cosine function (i.e. as a function ofwithfixed), and whose cross-section parallel to the-plane is a quadratic function (i.e. as a function ofwithfixed).

Find a surfacewhich is a possible model for the plant structure. Explain how your answer fits the requirements of the biologist.