Lesson 10 1 Circle and Circumference 10 1

Lesson 10 -1 Circle and Circumference 10 -1 – Circles and Circumference Lesson 8 -1: Circle Terminology 1

Circle Definition Circle : The set of points coplanar points equidistant from a given point. The given point is called the CENTER of the circle. The distance from the center to the circle is called the RADIUS. . . A Name the Circle : ○ A circle is always named with the center, example Circle A or using the symbol above Lesson 8 -1: Circle Terminology A 2

Definitions Chord : The segment whose endpoints lie on the circle. Diameter : A chord that contains the center of the circle. Tangent : A line in the plane of the circle that intersects the circle in exactly one point. Point of Tangency : The point where the tangent line intersects the circle. Secant : A line that contains a chord. Lesson 8 -1: Circle Terminology 3

Example: In the following figure identify the chords, radii, and diameters. B Chords: AB, CE, BF C A O D F E Radii: BO, DO, FO Diameter: BF Lesson 8 -1: Circle Terminology 4

Examples l l l . Name the circle: E A Name radii of the circle: AE, BE, DE, CE Name chords of the circle: AB, DC, Name diameters of the circle: AC, BD Find AE if BD is 10 meters. 5 Find AE and BD if EC is 3 meters. D AE= 3, BD = 6 Lesson 8 -1: Circle Terminology B E C 5

CIRCUMFERENCE: Circumference is the distance around the circle. Formula: Or where Example: Find the circumference of the following circle. 3 cm 6 Π cm Lesson 8 -1: Circle Terminology 6

The radius, diameter, or circumference of a circle is given. Find the missing measures to the nearest hundredth. l r = 4 cm, d = 8 C = 8 π l d = 6 ft, r = 3, C = 6 π l C = 8Π, r = 4, d = 8 l C = 13. 699 r = 2. 18, d = 4. 36 Lesson 8 -1: Circle Terminology 7

Find the exact circumference of each circle. 5 cm 12 cm 2 cm Lesson 8 -1: Circle Terminology 8