1. The problem is to understand the term "circulus" which is Latin for "circle". 2. A circle is a set of points in a plane that are all at the same distance (radius) from a fixed point (center). 3. The formula for the circumference (perimeter) of a circle is $$C = 2\pi r$$ where $r$ is the radius. 4. The formula for the area of a circle is $$A = \pi r^2$$. 5. These formulas are fundamental in geometry and are used to calculate properties of circles. 6. If you have a specific problem involving a circle, please provide the details for further assistance.