A function has a spinode (also called a horizontal cusp) at a point if is continuous at and
from one side while
from the other side, so the curve is continuous but the derivative is not.s
A function has a spinode (also called a horizontal cusp) at a point if is continuous at and
from one side while
from the other side, so the curve is continuous but the derivative is not.s
Weisstein, Eric W. "Spinode." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Spinode.html