The reason is that the radius cannot be determined by the movement of both feet.

The way to draw a circle is to fix it in one place with one foot, which is a basic point and symbolizes a main line in the learning process.

Compass is a tool for drawing circles or strings in mathematics and drawing, and is often used for drawing with a ruler. Compass is a tool used to draw circles or arcs in mathematics and drawing. Compasses are usually made of metal.