A circle is a perfectly round 2D shape where every point along the boundary is equidistant from a fixed central point called the center. It is one of the most fundamental and symmetrical geometric shapes, frequently encountered in both natural and human-made structures.
The total distance around the circle (perimeter):
\[ P = 2 \pi r = \pi d \]
where:
The area enclosed within the boundary of the circle:
\[ A = \pi r^2 = \frac{\pi d^2}{4} \]
where: