Circle Caustic
Consider a point light source located at a point 
. The Catacaustic of a unit Circle for the light at 
is the Nephroid
 |  |  | (1) |
 | |  | (2) |
The Catacaustic for the light at a finite distance
is the curve | |  | (3) |
| |  | (4) |
and for the light on the Circumference of the Circle
is the Cardioid | |  | (5) |
| |  | (6) |
If the point is inside the circle, the catacaustic is a discontinuous two-partcurve. These four cases are illustrated below.
The Catacaustic for Parallel rays crossing a Circle is a Cardioid.
See also Catacaustic, Caustic- Knot Curve
- Knot Determinant
- Knot Diagram
- Knot Exterior
- Knot Linking
- Knot Polynomial
- Knot Problem
- Knot Shadow
- Knot Sum
- Knot Theory
- Knot Vector
- Knödel Numbers
- Kochansky's Approximation
- Koch Antisnowflake
- Koch Island
- Koch Snowflake
- Koebe Function
- Koebe's Constant
- Kollros' Theorem
- Kolmogorov-Arnold-Moser Theorem
- Kolmogorov Complexity
- Kolmogorov Constant
- Kolmogorov Entropy
- Kolmogorov-Sinai Entropy
- Kolmogorov-Smirnov Test