Circles

• set of points on a plane

  circle
• fixed distance


  circle
• fixed point


  center
• from center to any point on the circle


  radius
• endpoints lie on the circle

  chord
• pass through the center

  diameter
• A diameter is a chord, but a chord is NOT NECESSARILY a diameter
• same center, different radii

  concentric circles
• same radii length

  congruent circles
• angle with a vertex that is at the center or the circle

  central angle
• half a circle, denoted with 3 capital letters

  semicircle
• radius is less than

  interior
• radius is greater than

  exterior
• denoted with 2 capital letters, less than 180 degrees


  minor arc
• denoted with 3 capital letters, greater than 180 degrees

  major arc
• 2 arcs, same circle, one common point

  adjacent arcs
• add the two adjacent arcs

  arc addition postulate
• polygon with all vertices on the circle

  inscribed polygon
• circumscribed circle around/about a polygon


  circumcircle
• angle whose vertex contains chords of the circle

  inscribed angle
• endpoints are on the side of the angle


  intercepted arc
• inscribed angle is half of its intercepted arc

  inscribed angle theorem
• right angle


  corollary 3.1
• 2 inscribed angles are congruent


  corollary 3.2
• supplementary

  corollary 3.3