CCGPS Geometry Day 20 9 4 13 UNIT

CCGPS Geometry Day 20 (9 -4 -13) UNIT QUESTION: What special properties are found with the parts of a circle? Standard: MMC 9 -12. G. C. 1 -5, G. GMD. 1 -3 Today’s Question: How do we use angle measures to find measures of arcs? Standard: MMC 9 -12. G. C. 2

AGENDA 1. 2. 3. 4. Notes on Circles Notes on Central Angles Practice Worksheet Homework Worksheet

C Parts of a Circle – set of all points _____ equidistant from a given point called the _____ center of the circle. Symbol: C

CHORD: A segment whose endpoints are on the circle

Radius RADIUS: P Distance from the center to point on circle

DIAMETER: Distance across the circle through its center Diameter P Also known as the longest chord.

Use P to determine whether each statement is true or false. Q R P T S

Secant Line: intersects the circle at exactly TWO points

Tangent Line: a LINE that intersects the circle exactly ONE time Forms a 90°angle with a radius Point of Tangency: The point where the tangent intersects the circle

Name the term that best describes the notation. t n a Sec s u i d Ra Diamet e r Ch or d n a T t n ge

Central Angle : An Angle whose vertex is at the center of the circle A Major Arc Minor Arc More than 180° Less than 180° P ACB To name: use 3 letters C AB B APB is a Central Angle To name: use 2 letters

Semicircle: An Arc that equals 180° E D To name: use 3 letters EDF P F

THINGS TO KNOW AND REMEMBER ALWAYS A circle has 360 degrees A semicircle has 180 degrees Vertical Angles are Equal

measure of an arc = measure of central angle A E Q m AB = 96° m ACB = 264° m AE = 84° 96 B C

Arc Addition Postulate A C B m ABC = m AB + m BC

Tell me the measure of the following arcs. m DAB = 240 m BCA = 260 D C 140 R 40 100 80 B A

Congruent Arcs have the same measure and MUST come from the same circle or of congruent circles. C B A 45 45 D 110 Arc length is proportional to “r”

Classwork • Practice Worksheet

Homework: • Practice Worksheet