A circle is a shape consisting of all points in a plane that are a given distance from a given point, the centre; equivalently it is the curve traced out by a point that moves in a plane so that its distance from a given point is constant. A circle is the same as 360°. You can divide a circle into smaller portions. A part of a circle is called an arc, and an arc is named according to its angle.
The diameter of a circle is the longest chord of a circle. Equal chords and equal circles have equal circumference. The radius drawn perpendicular to the chord bisects the chord. Circles having different radius are similar. The chords that are equidistant from the centre are equal in length.
Because of their symmetry, circles were seen as representations of the “divine” and “natural balance” in ancient Greece. Later on, the shape would become a vital foundation for the wheel and other simple machines. A focus on circles is evident among structures built throughout history. In this chapter, students will learn the basic types and parts of a circle, cyclic properties and some important theorems and results.