RS Aggarwal Solutions for Class 9 Chapter 12 “Circles”, 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. The distance between the midpoint and the circle border is called the radius. A line segment that has the endpoints on the circle and passes through the midpoint is called the diameter. Circles are mainly used in the construction of high rise buildings and in creating maps. The examples of circles in real life are pizzas, camera lenses, steering wheels, buttons and satellite’s orbit etc. This Chapter has important topics like some of the terms related to a Circle, arcs of a Circle, congruence, angles subtended by arcs and results on quadrilaterals.