# Circles

**COOO.OOO** is mainly circles, and I've done a lot of work on circles. My **circle-sphere calculator** returns the area, circumference, radius, and diameter of a circle. And the volume and surface area of the corresponding sphere. From *any* starting point. So, if you know the volume of a sphere you can quickly get the surface area or diameter. I built it for myself when I was checking the sizes of viral cores (I did many **viral graphics** that needed 3D models built to scale). I've also done animations illustrating some mathematical properties of circles and spheres:

Circles are buried in many things, as illustrated in my animations of sine waves, cosine waves, tan waves, and circular polarisation: