### Unit 8: Circles

Circles are everywhere you look, for example, tires, pools, fans, and watches. You can probably think of several more items that are circular. In this unit, you will learn about circles and arcs, which are slices of the edge of a circle.

Believe it or not, arcs are used a lot in real life. The feet of a rocking chair are arcs; the crust on a slice of pizza is an arc. Anything that looks like an incomplete circle is an arc. How are these arcs made? What kinds are there? How can we measure them? These are questions that you will explore in this unit.

**Completing this unit should take you approximately 10 hours.**

Upon successful completion of this unit, the student will be able to:

- identify the various parts of a circle;
- determine arc lengths of a circle; and
- determine the measure of angles created by lines intersecting a circle.

### 8.1: Language and Notation of a Circle

Take notes as you watch this video to understand the language and notation associated with a circle. Watch this presentation carefully two or three times to understand how to identify parts of a circle.

Take notes as you watch the videos and read this section to learn about how to recognize various parts of a circle. Then, complete the practice problems. These exercises will provide you with the opportunity to recognize various parts of a circle.

### 8.2: Tangent Lines

Take notes as you watch the videos and read this section to learn how to identify tangent lines and their properties. Then, complete the practice problems. These questions will provide you with the opportunity to apply properties of tangent lines and circles.

### 8.3: Arcs in Circles

Take notes as you watch the videos and read this section to learn about arcs in a circle. Then, complete the practice problems. These exercises will provide you with the opportunity to recognize various parts of a circle.

### 8.4: Chords in Circles

Take notes as you watch the videos and read this section to learn about how to recognize chords. Then, complete the practice problems. These exercises will provide you with the opportunity to apply theorems related to chords.

### 8.5: Inscribed Angles

Take notes as you watch the videos and read this section to learn about inscribed angles in circles and their properties. Then, complete the practice problems. These exercises will provide you with the opportunity to apply properties of inscribed angles.

### 8.6: Angles of Chords, Secants, and Tangents

Take notes as you read this section to learn about inscribed angles of chords, secants, and tangents. Then, complete the practice problems. These exercises will provide you with the opportunity to apply properties of angles of chords, secants, and tangents.

### 8.7: Segments of Chords, Secants, and Tangents

Take notes as you read these sections to learn about segments of chords, secants, and tangents. Then, complete the practice problems. These questions will provide you with the opportunity to apply properties of segments of chords, secants, and tangents.