1. Unit 4: Unit 4: Circles and Volume Introduction to Circles

2. Instructions You will view the PowerPoint independently Write down the vocabulary and Illustrations for each term Check for understanding with the Practice Questions Set A – E (Make sure these examples are in your composition notebook) See me with any questions You have 20 minutes to complete!!

3. Circle Vocabulary

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

5. CHORD: A segment whose endpoints are on the circle

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

7. P RADIUS: Distance from the center to a point on the circle

8. Formula Radius = ½ diameter or Diameter = 2r

9. D = ? r = ? D = ? Set A Guided Practice Questions Set A

10. Use  P to determine whether each statement is true or false. P Q R T S Set B Guided Practice Questions Set B

11. Secant Line: intersects the circle at exactly TWO points

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

13. Name the term that best describes the notation. Secant Radius Diameter Chord Tangent Set C Guided Practice Questions Set C

14. Central Angles An angle whose vertex is at the center of the circle

15. P A B C 3 Types of Arcs Minor Arc Major Arc Less than 180° More than 180° AB ACB To name: use 2 letters To name: use 3 letters  APB is a Central Angle

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

17. THINGS TO KNOW AND REMEMBER ALWAYS A circle has 360 degrees A semicircle has 180 degrees Vertical Angles are CONGRUENT Linear Pairs are SUPPLEMENTARY

18. Formula measure Arc = measure Central Angle

19. m AB m ACB m AE A B C Q 96  E = = = 96° 264° 84° Find the measures. EB is a diameter. Set D Guided Practice Questions Set D

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

21. Tell me the measure of the following arcs. AC is a diameter. 80  100  40  140  A B C D R m DAB = m BCA = 240  260  Set E Guided Practice Questions Set E

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