1. CMB 2011 (vol 54 pp. 706)
|Nonconstant Continuous Functions whose Tangential Derivative Vanishes along a Smooth Curve|
We provide a simple example showing that the tangential derivative of a continuous function $\phi$ can vanish everywhere along a curve while the variation of $\phi$ along this curve is nonzero. We give additional regularity conditions on the curve and/or the function that prevent this from happening.