For the practical use of Calculus

How do you figure out the function of a particular curve of a real-life object that isn't a circle or something simple like that?

What if I had an elliptical-shaped wing that isn't a perfect ellipse? How do I find the wing area of that object? I know I can "cheat" and just break up the wing into smaller trapezoids, but that's not what I'm here for.

I've always wondered about how people figure out the function of the curve of some real-life object.

>>8
That gives EXISTENCE of polynomial approximations to continuous functions, not a way to find them.  You can construct them if you already know what the original function is, for example using Taylor series.  If I give you an arbitrary curve you can't use the Stone-Weierstrass theorem to find a polynomial that fits it; you would need to use a computer to find some interpolating curve.  That curve would NOT be just a truncated power series; if you try to use high order polynomials for practical interpolation, you run into major problems; see http://en.wikipedia.org/wiki/Runge%27s_phenomenon.