Circle Vocabulary

Circle Vocabulary – Completed Copy Circle Circle: The set of all points in a plane that are equally distant from a center point. A The equal distance that all points are from the center is the length of the radius. A circle is named by the center point of the circle. Circle A Example B C A D F E AF = 5 DA = 5 DF = 10 CA = 5 BA = 5 BE = 10 Note: All radii in a circle are congruent. Chord whose endpoints lie on a circle. 𝐴𝐵 is a chord of circle Q. D Give two examples of diameters in circle A: A F 𝐷𝐹 E 𝐵𝐸 Secant J If QMN @ NQM, then name two congruent chords: K Q 𝐽𝐾 is a secant of Circle Q. M 𝑀𝑁 @ 𝑁𝑄 N Diameter: The longest chord in a circle. This D chord must include the Q center of the circle. The C length of a diameter is twice the length of the 𝐶𝐷 is a diameter radius. Diameter C 𝐴𝐵 is a radius of circle A. If mQMN = mNQM = 80, then mQNM = 20 Example: Given Circle A B A Example segment Q B Q Chord – a B A Radius: The segment that connects the center of the circle to any point on the circle. The plural of radius is radii. Radius In circle A, the length of the radius is 5. Find each: of circle Q. Secant: A line that contains a chord. This line will pass through two points on a circle. Example B Name an example of a secant: 𝐴𝐵 A Name an example of a chord: 𝐴𝐵 C A If 𝐴𝐵 is a tangent to the circle, then C is a point of tangency. Tangent: A line that intersects a circle at exactly one point. The point of intersection is called the point of tangency. Central A D Angle: an angle with its vertex at the CAD is a center of the central angle circle. Example C D A F 𝐺𝐻 E H R T QRT is an inscribed angle. Semicircle B F is a point of tangency, name a tangent: G Q Inscribed Angle: An angle whose vertex is on the circle. for circle A Minor Arc B Inscribed Angle C Central Angle Tangent Point of Tangency B C B Major Arc K 30° L A J A Minor Arc: An arc that measures less than 180. ෢ is a minor arc. Ex: 𝑨𝑩 Semicircle: An arc that measures exactly 180. Ex: If 𝑨𝑪 is a diameter, then ෣ 𝑨 𝑩𝑪 is a semicircle. Major Arc: An arc that measures more than 180. ෢ is a major arc. Ex: 𝑱𝑲𝑳 Semicircles & Major Arcs MUST be named with 3 letters. Minor Arcs can be named with 2 To find a measure, trace the letters given IN ORDER! or 3 letters. Note: Arc measures are measured in degrees. If you create arcs that complete an entire circle, the arcs sum to 360. Example: JG is a diameter F 60° 40° Name an example of each: ෢ Minor Arc: 𝐾𝐹 G ෢ Semicircle: 𝐽𝐹𝐺 ෣ Major Arc: 𝐹 𝐺𝐾 70° K Find the measure of each arc: 80° J H 110° ෢ = 100 m𝐾𝐺 ෣ = 170 m𝐾𝐺𝐻 ෢ = 190 m𝐾𝐽𝐻 ෢ = 180 m𝐽𝐹𝐺 ෢ = 70 m𝐺𝐻 ෢ = 320 m𝐾𝐽𝐹 Circle Circle Vocabulary Example B C A D Radius In circle A, the length of the radius is 5. Find each: AF = ____ DA = _____ F DF = ____ CA = _____ E BA = ____ BE = _____ Note: All radii in a circle are congruent. Chord B A Q Chord – a segment whose endpoints lie on a circle. AB is a chord of circle Q. Example Q If QMN @ NQM, then name two congruent chords: M N ______ @ ______ If mQMN = mNQM = 80, then mQNM = _____ Example: Given Circle A D B A E Diameter C Give two examples of diameters in circle A: F _________ _________ Secant Example B Name an example of a secant: _______ A Name an example of a chord: ________ Tangent Point of Tangency Example C D B A G F F is a point of tangency, name a tangent: ________ E H Central Angle Inscribed Angle Minor Arc Semicircle Major Arc Semicircles & Major Arcs MUST be named with 3 letters. Minor Arcs can be named with 2 To find a measure, trace the letters given IN ORDER! or 3 letters. Note: Arc measures are measured in degrees. If you create arcs that complete an entire circle, the arcs sum to 360. Example: JG is a diameter F 60° 40° Name an example of each: Minor Arc: _______ G Semicircle: _______ Major Arc: _______ 70° K Find the measure of each arc: 80° J H 110° ෢ = _______ m𝐾𝐺 ෢ = ______ m𝐽𝐹𝐺 ෣ = ______ m𝐾𝐺𝐻 ෢ = _______ m𝐺𝐻 ෢ = _______ m𝐾𝐽𝐻 ෢ = _______ m𝐾𝐽𝐹