Introduction to Circles in Geometry

Circles Intro

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Parts of a Circle

• Center of a Circle EX: A

• A radius is a segment whose endpoints are the center and any point on the circle. EX: HA or FA

• The diameter is a chord that contains the center of the circle. EX: HF

• A chord is a segment whose end points are on the circle. EX: DG

• A secant is a line that intersects a circle at two points. EX: BD

• A tangent is a line in the plane of a circle that intersects the circle in exactly one point. EX: JB

• A ​point of tangency is where the tangent and circle intersect. EX: H

Multiple Choice

PR is an example of a ____

• secant

• tangent

• diameter

• radius

Multiple Choice

Line k is an example of a ______

• tangent

• secant

• chord

• radius

Multiple Choice

What is an example of a point of tangency?

• A

• F

• H

• B

Multiple Choice

Line j is an example of a ______

• chord

• tangent

• diameter

• secant

Multiple Choice

How many common tangents do the circles have?

• 1

• 2

• 3

• 4

Multiple Choice

How many common tangents do the circles have?

• 0

• 1

• 2

• 3

Multiple Choice

How many common tangents do the circles have?

• 1

• 2

• 3

• 4

Determining if a line is tangent to a circle

A tangent to a circle will be perpendicular to the radius of a circle at the point of tangency

Tangent segments of a circle with the same external endpoint are congruent