1. Skills #2 1. What symbol is used to name circle M?
2. The distance from the center to a point on a circle is __________.
3. The distance across a circle through the center is a ___________.
4. A chord is a segment whose _________ are on the circle.
5. A secant is a line that intersects at circle in _______ points.
6. A tangent is a line that intersects a circle at exactly ________ point(s).
7. The point where a tangent intersects a circle is a _____________.
8. A tangent is ___________ to a radius of the circle.
9. If 2 tangent lines originate at the same external point, the tangents are ______________.
10. A common internal tangent intersects the segment between the ________________ of a circle.

2. 26. Central Angles and Arcs

3. Central Angles and Arcs
Std- MM2G3 – Understand properties of circles
Essential Question – How are the angles made by arcs and chords related?

4. Central angle
Central angle- angle whose vertex is the center of a circle A
ACB is a central angle C B

5. Arcs Arc- a piece of a circle. Named with 2 or 3 letters
Measured in degrees B ( BP P

6. Major and minor arcs
Minor arc- part of a circle that measures less than 180o (named by 2 letters).
Major arc- part of a circle that measures between 180o and 360o.
(needs three letters to name) ( AC (
ABC

7. Arc measures Measure of a minor arc- measure of its central angle
Measure of a major arc- 360o minus measure of minor arc

8. Ex: find the arc measures(
m AB=
m BC=
m AEC=
m BCA=
50o (
130o ( A
180o
180o D (
180o+130o = 310o
50o
130o C
OR 360o- 50o = 310o B

9. Arc addition
The measure of an arc formed by two adjacent arcs is the sum of the measures of those arcs. B A ( ( ( C
m ABC = m AB+ m BC

10. Congruent arcs Congruent arcs- 2 arcs with the same measure
MUST be from the same circle OR  circles!!!

11. Example (
m AB=30o A (
m DC=30o E
30o B D ( (
30o DC C

12. Example ( ( ( ( m BD= 45o A m AE= 45o B BD @ AE
The arcs are the same measure; so, why aren’t they ?
45o C D E
The 2 circles are NOT  !