1. The problem is to show the diagram of a circle. 2. A circle is defined as the set of all points in a plane that are at a fixed distance (radius) from a fixed point (center). 3. The standard equation of a circle with center at the origin $(0,0)$ and radius $r$ is: $$x^2 + y^2 = r^2$$ 4. This equation means that for any point $(x,y)$ on the circle, the sum of the squares of its coordinates equals the square of the radius. 5. Since you requested a diagram, the function to plot is: $$y = \pm \sqrt{r^2 - x^2}$$ which represents the upper and lower semicircles. 6. This is a fundamental geometric shape and can be graphed using graphing tools like Desmos.