Circles are also are pieces of many 3D shapes like cones, cylinders, and spheres. If we were to begin to name objects that we see everyday that included these 3D shapes as well we could go on and on.
The study of circles has lead to many important discoveries in both geometry and calculus. One important contribution of the study of the area of circles is integration. (Hendrickson, 2013) (Click on this link to go to an applet that will help you come to discover how the study of circles lead to integration. Here is an activity plan and a task sheet to go along with the applet.) The properties of circles have also been used to build famous buildings like the Colosseum and the domes found on many churches and capital buildings. Circular structures like the Colosseum allowed everyone to view the arena below. (Mastrigli, 2009) This same structure is seen today in many different sport arenas.
The Olympic rings symbolize the unity of the five continents. There is no beginning and no end to a circle. Each point on the curve is equidistant from the center, which symbolizes equality and unity. The circle in ancient cultures represented the Sun, which was a symbol of life. Many people today wear wedding rings to symbolize their unity in marriage.
Another common symbolic circle is the Yin and Yang symbol. It symbolizes the balance in life and nature. The curves in this circle flow into each other showing the perfect balance. This circle displays perfect symmetry.
Circles can be used to find the area of spheres, to discover the areas of other polygons, or to create useful objects like tires, rings, sports arenas and lenses in microscopes.
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