Parts of Circles Dictionary + pictures

Circle- The set of points equidistant from a given point (the center)

Radius- A segment with endpoints at the center and on the circle

Chord- A segment with endpoints on the circle

Diameter- A chord that passes through the center (Diameter = 2 radius)

Secant- A line that intersects the circle in two places

Tangent- A line that intersects the circle at exactly one place

Point of Tangency- The point at which the tangent line intersects the circle

Central Angle- An angle with a vertex at the center, and two sides that are radii

Inscribed Angle- An angle with a vertex on the circle, and two sides that are chords

Arc- A portion of the edge of the circle defined by two endpoints

Minor arc- An arc with a measure less than 180

*Use 2 letters to name it

Major arc- An arc with a measure greater than 180

*Use 3 letters to name it

Semicircle- An arc with endpoints on the diameter

*Always equal to 180

Area Fromula

π r 2

Circumference Formula

2 π r

Arc Length

l=x(x)c/360