Blumenthal, Leonard M. Formerly, Department of Mathematics, University of Missouri, Columbia, Missouri.
Frame, J. Sutherland Formerly, Department of Mathematics, Michigan State University, East Lansing, Michigan.
Last reviewed:February 2019
Show previous versions
- Development of π
- Nine-point circle theorem
- Additional Reading
The curve that is the locus of points in a plane with equal distance from a fixed point. One of the most basic geometric figures, a circle is perfectly round. In elementary mathematics, "circle" often refers to the finite portion of the plane bounded by a curve, known as the circumference. All points along the circumference are equidistant from a fixed point of the plane at the circle's center; the line connecting the center to any point on the circumference is called a radius. Two radii spanning the width of a circle are called a diameter (Fig. 1). Pi (π) is the ratio of a circle's circumference to its diameter, expressed in decimal form typically only to the hundredths place as 3.14. Circles are conic sections, defined analytically by certain second-degree equations in Cartesian coordinates. See also: Analytic geometry; Canonical coordinates and transformations; Cone; Conic section; Geometry; Mathematics; Plane geometry
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information