• ### Unit 8: Circles

In this unit, we will explore circles and arcs, which are slices of the edge of a circle. We use arcs to describe anything that looks like an incomplete circle, such as the feet of a rocking chair or the crust of a slice of pizza. We will learn to classify and measure arcs in this unit.

Completing this unit should take you approximately 3 hours.

• ### 8.1: Language and Notation of a Circle

Before we can begin studying calculations involving circles, we need to understand the definitions and notation we use to describe circles and circular objects.

• ### 8.2: Tangent Lines

We can draw special lines called tangent lines on circles. A tangent line touches the circle at only one point, and is perpendicular to the radius of the circle drawn to the point where the tangent line touches the circle.

• ### 8.3: Arcs of Circles

An arc is a section of a circle.

• ### 8.4: Inscribed Angles

An inscribed angle occurs inside a circle. The angle's vertex is on the circle and the rays of the angle are chords (lines within the circle) of the circle.

• ### 8.5: Angles of Chords, Secants, and Tangents

Now, we put together what we have learned to calculate more advanced trigonometric ratios. First, we need to study the meaning of chords, or line segments that exist within a circle.