2 problems

Let $a<b$ and let $\epsilon$ satisfy … Consider the surface … An umbilic point is a point where the principal curvatures coincide, and its index is the index of the principal direc…

Let $a,b,c>0$ and let $k\in\mathds{Z}_{>1}$. Consider the surface … An umbilic point is a point where the principal curvatures coincide, and its index is the index of the principal…