Cusp
A cusp is a point on a continuous curve where the tangent vector reverses sign as the curve is traversed. A function 
has a cusp (also called a Spinode) 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. A cusp is atype of Double Point. The above plot shows the curve 
, which has a cusp at the Origin.
References
Walker, R. J. Algebraic Curves. New York: Springer-Verlag, pp. 57-58, 1978.
- Joint Distribution Function
- Joint Probability Density Function
- Joint Theorem
- Jonah Formula
- Jones Polynomial
- Jonquière's Function
- Jordan Algebra
- Jordan Curve
- Jordan Curve Theorem
- Jordan Decomposition Theorem
- Jordan-Hölder Theorem
- Jordan Measure
- Jordan Polygon
- Jordan's Inequality
- Jordan's Lemma
- Josephus Problem
- Jug
- Jugendtraum
- Juggling
- Julia Fractal
- Julia Set
- Jump
- Jump Angle
- Jumping Champion
- Jung's Theorem