Create a data frame for a circle marking the curvature of a function.
inscribed_circle(ftilde, x0 = 0)inscribed_circle() return a data frame with x and y components describing the inscribed circle
located at the point $(x_0, f(x_0))$. Plot this with gf_path(y ~ x)
curvature_function() returns a function that gives the curvature of the specified
function for any input $x$. It's much like D() in the way it is used.
A tilde expression defining a function
The value for the input at which the curvature is to be calculated.