• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
Geometry Help
  • About
  • Privacy Policy
  • Contact Me
  • Terms of Service
  • Accessibility Statement
menu icon
go to homepage
search icon
Homepage link
  • About
  • Privacy Policy
  • Contact Me
  • Terms of Service
  • Accessibility Statement
×

Circles

In geometry, a circle is defined as the collection of all points that are the same distance from one point, which is the center of the circle.

Circles in Geometry

The distance from the center of the circle to any point on the circle is called the radius, and commonly written 'r'.

If we draw a line from one point on the circle, through its center and on to another point on the circle, directly across from the first point, that line's length will be 2 times r, and is called the circle's diameter, 'd'. d= 2*r

A circle is a geometric shape completely defined by its radius- knowing the radius we can calculate the circle's area, and its circumference.

A circle's circumference, C, is Ccircle=2*π*r (where r is the radius) , and since the diameter, d, is 2 times r, we can also write Ccircle=d*π

A circle's area is given by the formula Acircle=π*r2

--
Now that we've explained the basic concept of circles in geometry, let's scroll down to work on specific geometry problems relating to this topic.

circle inscribed in equilateral triangle

Area of a Circle Inscribed in an Equilateral Triangle

Geometry drawing: congruent chords

Congruent Chords are Equidistant from the Center

two parallel chords

A Diameter that Bisects Two Chords

Diameter perpendicular to a chord

A Diameter Perpendicular to a Chord

Diameter perpendicular to a chord

A Diameter Bisecting a Chord

Inscribed triangle with diameter

Radius of a Circle with an Inscribed Triangle

Geometry shape: diamond with diagonals

Inscribed Shapes: Opposing Angles of a Quadrangle Inscribed in a Circle

Geometry shape of a polygon inscribed in a circle

Polygon Inscribed in a Circle

Intersecting chords in geometry

Intersecting Chords Theorem

central angle in geometry

Proving the Inscribed Angle Theorem

two tangent theorem in geometry

The Two Tangent Theorem

Geometry: arc in a circle

Arc Length Formula

  • « Go to Previous Page
  • Go to page 1
  • Go to page 2

Primary Sidebar

About

Welcome to Geometry Help! I'm Ido Sarig, a high-tech executive with a BSc degree in Computer Engineering and an MBA degree in Management of Technology. I'm here to tell you that geometry doesn't have to be so hard! My goal with this website is to help you develop a better way to approach and solve geometry problems, even if spatial awareness is not your strongest quality. Read More…

Geometry Topics

  • Area of Geometric Shapes
  • Circles
    • Arcs, Angles, and Sectors
    • Chords
    • Inscribed Shapes
    • Tangent Lines
  • Lines and Angles
    • Intersecting Lines and Angles
    • Parallel Lines
    • Perpendicular lines
  • Pentagons and Hexagons
  • Perimeter of Geometric Shapes
  • Polygons
  • Quadrangles
    • Kites (Deltoids)
    • Parallelograms
    • Rectangles
    • Rhombus
    • Squares
    • Trapezoids
  • Triangles
    • Congruent Triangles
    • Equilateral Triangles
    • Isosceles Triangles
    • Pythagorean Theorem
    • Right Triangles
    • Similar Triangles
    • Triangle Inequalities

By accessing or using this website, you agree to abide by the Terms of Service and Privacy Policy.


Copyright © 2023