 Chord error bound

If a twice differentiable parametric curve $R:[a,b]\to {\mathbb{R}}^m$ satisfies $\Vert R^{\prime \prime }\Vert \le M$, its deviation from the linearly parameterized chord is at most $M(b-a{)}^2/8$. This follows from the Green function for the second derivative with zero endpoint values. It bounds the Hausdorff distance between the arc and its chord.

// Target: analysis.bigb